## 1. Generics and Logical Form



In English, generics can be expressed using a variety of syntactic
forms: *bare plurals* (e.g., "tigers are striped"),
*indefinite singulars* (e.g., "a tiger is
striped"), and *definite singulars* ("the tiger is
striped"). However, none of these syntactic forms is dedicated
to expressing generic claims; each can also be used to express
existential and/or specific claims. Further, some generics express
what appear to be generalizations over individuals (e.g.,
"tigers are striped"), while others appear to predicate
properties directly of the kind (e.g., "dodos are
extinct"). These facts and others give rise to a number of
questions concerning the logical forms of generic statements.


### 1.1 Isolating the Generic Interpretation



Consider the following pairs of sentences:



(1)


a.
Tigers are striped.
b.
Tigers are on the front lawn.
 
(2)


a.
A tiger is striped.
b.
A tiger is on the front lawn.
 
(3)


a.
The tiger is striped.
b.
The tiger is on the front lawn.
 


The sentence pairs above are *prima facie* syntactically
parallel--both are subject-predicate sentences whose subjects
consist of the same common noun coupled with the same, or no, article.
However, the interpretation of first sentence of each pair is
intuitively quite different from the interpretation of the second
sentence in the pair. In the second sentences, we are talking about
some particular tigers: a group of tigers in
 (1b),
 some individual tiger in
 (2b),
 and some unique salient or familiar tiger in
 (3b)--a
 beloved pet, perhaps. In the first sentences, however, we are saying
something *general*. There is/are no particular tiger or tigers
that we are talking about.



The second sentences of the pairs receive what is called an
existential interpretation. The hallmark of the existential
interpretation of a sentence containing a bare plural or an indefinite
singular is that it may be paraphrased with "some" with
little or no change in meaning; hence the terminology
"existential reading". The application of the term
"existential interpretation" is perhaps less appropriate
when applied to the definite singular, but it is intended there to
cover interpretation of the definite singular as referring to a unique
contextually salient/familiar particular individual, not to a
*kind*.



There are some tests that are helpful in distinguishing these two
readings. For example, the existential interpretation is *upward
entailing*, meaning that the statement will always remain true if
we replace the subject term with a more inclusive term. Consider our
examples above. In
 (1b),
 we can replace "tiger" with "animal"
*salva veritate*, but in
 (1a)
 we cannot. If "tigers are on the lawn" is true, then
"animals are on the lawn" must be true. However,
"tigers are striped" is true, yet "animals are
striped" is false.
 (1a)
 does not entail that animals are striped, but
 (1b)
 entails that animals are on the front lawn (Lawler 1973; Laca 1990;
Krifka et al. 1995).



Another test concerns whether we can insert an adverb of
quantification with minimal change of meaning (Krifka et al. 1995).
For example, inserting "usually" in the sentences in
 (1a)
 (e.g., "tigers are usually striped") produces only a
small change in meaning, while inserting "usually" in
 (1b)
 dramatically alters the meaning of the sentence (e.g., "tigers
are usually on the front lawn"). (For generics such as
"mosquitoes carry malaria", the adverb
"sometimes" is perhaps better used than
"usually" to mark off the generic reading.)


### 1.2 Stage Level and Individual Level Predicates



Having distinguished two quite different meanings of these seemingly
similar sentence pairs, the question arises: what is the basis of
these two interpretations? This is of course a matter of debate, but
one important thesis is that it is the predicate that determines which
of the two readings the subject will receive, particularly in the case
of bare plural generics. In his 1977 dissertation, Greg Carlson argued
that the distinction between "stage level" and
"individual level" predicates is key here, and proposed
that stage level predications give rise to existential readings of
bare plurals and indefinite singulars, while individual level ones
give rise to generic readings. The distinction between the two types
of predicates can be drawn intuitively, and also on the basis of
linguistic patterns (Milsark 1974; Carlson 1977; Stump 1985).
Semantically, individual level predicates express properties that
normally are had by items for quite extended periods, often comprising
the items' whole existence. Stage-level predicates, on the other
hand, express properties normally had by items for relatively short
time intervals. Some examples of both types are as follows:



**Individual level predicates**
  

"is tall"; "is intelligent"; "knows
French"; "is a mammal"; "is female";
"is a singer"; "loves Bob"; "hates
Bob"



**Stage level predicates**
  

"is drunk"; "is barking"; "is speaking
French"; "is taking an exam"; "is
sober"; "is sick", "is sitting";
"is on the lawn", "is in the room".



Clearly the semantic distinction is not hard and fast: a teetotaler
may be sober for the entire course of his existence, and the
chronically ill may be sick for the entire course of theirs, and Alice
in Wonderland is tall at some times but short at others. In the normal
course of affairs, individual level predicates express more stable and
less temporally intermittent properties than stage level ones do.



The distinction also manifests itself linguistically. Stage level
predicates are permissible in the following constructions, while
individual level ones are not:



(4)
John saw Bill drunk/sober/sick/naked.
(5)
John saw Bill speaking French/taking an exam/smoking
cigarettes.
(6)
John saw Bill on the lawn/in the room.
(7)
\*John saw Bill intelligent/tall/a mammal/male.
(8)
\*John saw Bill knowing French/hating Bob.


There-insertion constructions behave similarly:



(9)
There are men drunk/sober/sick/naked.
(10)
There are men speaking French/taking an exam/smoking
cigarettes.
(11)
There are men on the lawn/in the room.
(12)
\*There are men intelligent/tall/mammals/male.
(13)
\*There are men knowing French/hating Bob.


Stage level predicates can be modified by locatives, while individual
level ones cannot:



(14)
John is drunk/speaking French/smoking in 1879 Hall.
(15)
\*John is a mammal/intelligent/male in 1879 Hall.
(16)
\*John knows French/hates Bob in 1879 Hall.


Carlson noted the difference in syntactic behavior between individual
and stage level predicates, and proposed that the distinction between
the classes of predicates underlies the distinction between
existential and generic readings of bare plurals:



(17)
Students are drunk/speaking French/on the lawn. (existential)
(18)
Students are intelligent/mammals/tall/male. (generic)
(19)
Students know French/hate Bob. (generic)


Stage level predicates appear to give rise to the existential reading
of bare plurals, while individual level ones give rise to generic
readings. Carlson also took the distinction to underwrite the
difference between existential and generic readings of the indefinite
singular:



(20)
A student is drunk/speaking French/on the lawn. (existential)
(21)
A student is intelligent/a mammal/tall/male. (generic)
(22)
A student knows French/hates Bob. (generic)


This seems to be correct, though there is more to say about the
indefinite singular in this regard. In particular, the indefinite
singular receives an existential interpretation even with individual
level predicates when the property attributed is "out of the
blue", or to a very unnatural kind. Yael Greenberg (2003) asks
us to note the contrast between the following pairs. Both statements
involve individual level predicates, and accordingly the bare plural
receives a generic interpretation. It is, however, very difficult to
interpret the following indefinite singular statements as anything
other than existential statements, conveying a remarkable fact about a
particular individual:



(23)
Famous semanticists sing German arias in the shower.
(24)
A famous semanticist sings German arias in the shower.
(25)
Tall, left-handed, brown-haired neurologists from France earn more
than $150,000 a year.
(26)
A tall, left-handed, brown-haired neurologist from France earns
more than $150,000 a year.


The contrast between stage level and individual level predicates would
thus seem to be insufficient to explain the availability of the
generic interpretation of indefinite singular statements.



It should further be noted that the distinction between stage level
and individual level predicates cannot explain the two readings of
definite singulars. If there is a salient tiger before us, an
utterance of "the tiger is intelligent" or "the
tiger is male" will easily be interpreted non-generically as
pertaining to the particular tiger in question, despite the fact that
these are individual level predications. The distinction is not
irrelevant here since it is true that stage level predications may
reliably give rise to non-generic interpretations, but clearly there
is more to story in the case of the definite singular.


### 1.3 Deriving Generic vs. Existential Interpretations



How exactly might the distinction between stage level and individual
level predicates give rise to existential vs. generic readings of bare
plurals? The original proposal is due to Greg Carlson (1977), however
Carlson himself later came to reject the basics of his account
(Carlson 1989). More recent discussion can be found in Diesing (1992),
Chierchia (1995), Kratzer (1995), Cohen and Erteschik-Shir (1997,
2002), Kiss (1998), and others.



In Carlson's original account, he proposed that stage level
predicates are lexically represented with existential quantifiers.
These quantifiers range over *realizations* of individuals.
Carlson's metaphysical outlook was as follows: the set of
individuals is composed of both objects (by which he meant regular,
everyday concrete items) and kinds. Both objects and kinds have
realizations. A realization of an object is a temporal slice thereof.
A realization of a kind is *either* an object that belongs to
the kind, or a temporal slice of such an object. Kinds are directly
denoted by bare plurals, on Carlson's view--that is, bare
plurals are singular referring terms, like names.



Consider now the predicate "is smoking". This is a stage
level predicate; on Carlson's view only stages (temporal slices)
of objects are ever smoking. Natural language, however, does not
supply temporal slices as objects of predication, but rather
individuals--at least on the surface. To resolve this mismatch,
the predicate "is smoking" would have to be lexicalized
as

 
\[ \lambda x \exists y(R(y,x) \mathbin{\&} \textrm{smokes}(y)) \]


"*R*" here means "is a realization of",
in Carlson's sense. The predicate can be applied to an object,
such as John, to yield:

 
\[ \exists y(R(y, j) \mathbin{\&} \textrm{smokes}(y)) \]


Thus (setting aside tense), "John is smoking" is true iff
some realization (i.e., temporal stage) of John is engaged in smoking.
The predicate can also be applied to kinds, as in "students are
smoking":

 
\[ \exists y(R(y, s) \mathbin{\&} \textrm{smokes}(y)) \]


Here "*s*" picks out the kind *student*, and
the sentence is true iff there are some realizations of the kind that
are engaged in smoking. (Recall that the realizations of the kind
*student* include *both* the particular individual
students *and* the temporal stages of those individual
students.) Thus we obtain the existential reading of the bare plural
in virtue of the lexical representation of stage level predicates.



Individual level predicates hold of individuals, not stages, and so
are directly predicated of their subjects. There is no inherent type
mismatch here, and so individual level predicates are lexicalized
without any such built-in quantifiers. As a first pass attempt at a
semantic formalization, Carlson took all individual level predicates
to be directly applicable to kinds, so "Cats like Bob"
would have as a logical form simply "\(\textrm{Like}(c,
b)\)". Carlson went on to note that this approach meets with
difficulties when faced with sentences such as "Cats like
themselves". "\(\textrm{Like}(c, c)\)" is does not
capture the appropriate truth conditions, since it corresponds only to
"cats like cats", and not to "cats like
themselves".



To deal with this, he introduces a monadic predicate operator \(G'\)
to take object-level predicates to kind-level predicates. "Cats
like themselves" would be formalized as "\(G'(\lambda x
(\textrm{Like}(x, x))(c)\)", which is to be understood as true
iff the object level predicate "\(\lambda x (\textrm{Like}(x,
x))\)" holds with sufficient regularity of the realizations of
the kind. Carlson took no stand on what this sufficient regularity
amounts to, other than to say that it is not the job of semantics to
tell us when an item satisfies a predicate containing
"\(G'\)", anymore than it is the job of semantics to tell
us when an item satisfies *any* predicate. Semantics tells us
that "John is red" is true iff John satisfies "is
red", which in turn holds iff John is red. Semantics does
*not* tell us *whether* John is red, nor how to go about
determining whether John is red. Whether an item has a property is not
a question for semantics.



Carlson later came to reject this account of the logical form of
generics--in particular, he came to reject the idea that there is
a one-place predicate operator such as \(G'\), and instead embraced
the idea that any generic operator should instead be two-place (1989).
This point is taken up below in the section on the logical form of
characterizing generics. First, though, it is helpful to draw a
distinction between two different kinds of generics.


### 1.4 Characterizing Generics and Direct Kind Predications



It is helpful to separate out two categories of generic statements.
Our first category includes statements such as "tigers are
striped", "ravens are black", "a lion has a
mane", and "the leopard has spots". These statements
are naturally thought of as expressing generalizations about
individual members of the kind. For example, we might suppose that
"tigers are striped" is made true by enough individual
tigers possessing stripes. The exact nature of these generalizations
is highly controversial.



In our second category, we have statements like "dinosaurs are
extinct", "the dodo is extinct", "tigers are
widespread", and "the domestic cat is common", which
are often thought to predicate a property directly of the kind in
question, rather than expressing generalizations concerning its
members. For example, in saying "dinosaurs are extinct",
one says something about the kind *dinosaur*, namely that that
kind of thing is extinct. We may notice that it is not possible to say
of an individual dinosaur, Dino, that Dino is extinct, since only a
kind can be extinct. Thus, for these generics, Carlson's
original idea--that bare plurals can refer directly to kinds, and
thus that (at least some) generics involve predicating properties
directly of kinds--remains widely accepted.



Examples of this second category are often referred to as
"direct kind predications" while examples of the first are
known as "characterizing generics". (Direct kind
predications are also known as D-generics ("D" for
"definite"); characterizing generics are also known as
I-generics ("I" for "indefinite") (Krifka
1987).) It should be noted that the indefinite singular form on its
standard interpretation cannot be used to express a direct kind
predication: statements such as "a dinosaur is extinct"
and "a tiger is widespread" are not felicitous. (They can
of course be heard as felicitous if they are given a very different
interpretation, so that their domain ranges over particular
kinds--e.g., "a dinosaur, namely the *T. rex*, is
extinct"--but this is not the relevant interpretation. To
see the difference, consider statements involving kinds that do not
themselves have salient subkinds, e.g., perhaps "a *T.
rex* is extinct".)



Much of the work on the semantics of generics has been focused on
characterizing generics, since they have proved the most elusive. It
is widely accepted that sentences like "dinosaurs are
extinct", "the dodo is extinct", and "tigers
are widespread" are singular statements that predicate
properties directly of kinds. For example, "tigers are
extinct" predicates the property of *being extinct*
directly of the kind *Panthera tigris*, and would be true just
in case *Panthera tigris* had the property of being extinct
(Krifka et al. 1995). The semantics of characterizing generics have
proved much less tractable.


### 1.5 The Logical Form of Characterizing Generics



For the remainder of this entry, we will be concerned only with
characterizing generics, since they have received the most attention,
and been the subject of most controversy. Henceforth, we will use the
term "generics" to mean specifically characterizing
generics. This section discusses the dominant theory of the logical
form of characterizing generics, and of necessity involves some
technical material.



It is generally agreed nowadays that, contra Carlson's earliest
work, there is a two-place operator, usually termed *Gen*,
which functions as an adverb of quantification (Lewis 1975). Adverbs
of quantification include "usually",
"generally", "typically",
"always", "sometimes", and so on. They
function to relate one set of conditions containing at least one free
variable to another set. Adverbs of quantification are, in
Lewis's sense, unselective, meaning that they bind any number of
free variables in the sentence, be they objects, events, or locations.
Consider, for example, the following sentence:



(27)
When *m* and *n* are positive integers, the power
\(m^n\) can always be computed by successive multiplication.


Following Lewis (1975), we should understand "always" as
relating the material in the when-clause to the material in the main
clause in following way:



(28)
Always *m*, *n* [*m* and *n* are
positive integers] [the power \(m^n\) can be computed by successive
multiplication]


This representation is based on Lewis's (1975) paper, and is
said to be a tripartite structure, consisting of a quantifier
*Q*, a Restrictor *R* (picking out the domain of
*Q*), and the Scope *S*, also called the matrix (picking
out the properties attributed to *Q* elements of *R*).
Tripartite structures take the form "*Q* [*R*]
[*S*]". The sentence represented by the tripartite
structure is true iff *Q* *R*s satisfy *S*.



In the above examples
 (27)
 and
 (28),
 the material from the when-clause is placed in the Restrictor, and
the material from the main clause is placed in the Scope. There are
two free variables in the Restrictor, namely *m* and
*n*, and so both are bound by the adverb of quantification
"always", which is naturally understood as a universal
quantifier.



Generics are most commonly assimilated to this model
**(**but see Nguyen, 2020). Carlson himself (1989)
rejected his original one-place generic operator, on the grounds that
it could not capture ambiguities as well as a two-place operator. He
considers the following sentence:



(29)
Typhoons arise in this part of the Pacific.


This has two distinct generic readings, which can be paraphrased as
follows:



(30)
Typhoons in general have a common origin in this part of the
pacific.
(31)
There arise typhoons in this part of the Pacific.


It would be a mistake to take the latter reading to be an existential
reading: it does not simply mean that there are some particular
typhoons that originated in the relevant location, but rather seems to
be saying something general about the relevant location: situations
involving that location are--with sufficient
regularity--situations involving the arising of typhoons. A
dyadic non-selective operator can easily accommodate both
readings:



(32)
\(\textit{Gen } x [\textrm{Typhoon}(x)]
[\textrm{Arises-in-this-part-of-the-pacific}(x)]\)
(33)
\(\textit{Gen } s [\textrm{In-this-part-of-the-pacific}(s)]
\exists y [\textrm{Typhoon}(y)\ \mathbin{\&}\)
\(\textrm{Arises-in}(y, s)]\)


The monadic operator can only yield the first (less natural)
interpretation:

 
\[G'(\textrm{arises-in-this-part-of-the-pacific}(x))(\textrm{typhoons}).\]


Schubert and Pelletier (1987) also offer compelling arguments in favor
of a dyadic generic operator.



In keeping with this proposal, a common assumption (Heim 1982; Kamp
1981; Kamp and Reyle 1993; Diesing 1992; Kratzer 1995; and many
others) is that indefinites such as bare plurals and indefinite
singulars contribute predicates with unbound variables to the logical
forms containing them. In the course of syntactic operations, the
material in the sentence is divided up into the restrictor and scope
(e.g., Diesing 1992). If the sentence contains a quantificational
adverb (e.g., "usually", "always"), then any
unbound variables in the restrictor are bound by that quantificational
adverb, as in example
 (28)
 above. However, if there is no quantificational adverb, the generic
operator *Gen* is introduced to bind those variables. Thus, to
take a simple example, the logical form of a sentence like
"ravens are black" may be given as follows:



(34)
*Gen* *x* [Ravens(*x*)]
[Black(*x*)]


Even theorists who do not agree with the assumption that indefinites
contribute just predicates and unbound variables to their logical
forms (see, e.g., Chierchia 1998) tend to agree that a tripartite
structure nonetheless is the correct analysis for generics. One
notable exception is David Liebesman (2011), who argues that
characterizing generics are themselves direct kind
predications--that, e.g., "tigers have stripes" is
best understood as simply the attribution of the predicate "have
stripes" to the kind *tigers.* (See also Cohen 2012;
Teichman 2016. Cohen argues that although pragmatic factors lead many
generics to ultimately receive reinterpretations involving Gen,
generics are always in the first instance kind predications.) It is
not clear, however, whether a view such as Liebesman's is able
to account for the full range of semantic data. Recall that sentences
such as "cats lick themselves" led Carlson (1977) to
introduce a G' operator to capture the dominant interpretation,
namely that individual cats lick themselves (i.e., their own
bodies)--an interpretation which is not captured by the logical
form Lick(cats, cats). Similar complications arise for generics
involving so-called donkey anaphora, e.g., "lions that see a
gazelle chase it". Without the additional structure provided by
an operator, it is not clear how these sentences can be adequately
captured (Leslie 2015a).



The term "generic" is sometimes extended to sentences such
as "Mary smokes after work", since these habitual
statements share various features with generics, although they do not
express generalizations concerning *kinds*. It is often
believed that these statements should be analyzed with *Gen*
(e.g., Lawler 1972; Schubert and Pelletier 1989; Krifka et al. 1995,
and many others):



(35)
*Gen* *e* [Relevant-event-involving-Mary(*e*)
& Occurs-after-work(*e*)]
[Event-of-Mary-smoking(*e*)]


For the remainder of this entry, the term "habitual"
rather than "generic" will be used for these
statements.


## 2. Semantic Analyses of *Gen*



A great deal of work has been done on the semantics of
(characterizing) generics, particularly on bare plural
(characterizing) generics. It is easy to see why this is so:
"Ducks lay eggs" is a true generic, while "ducks are
female" is false, yet it is only the female ducks who ever lay
eggs. "Mosquitoes carry the West Nile virus" is true, and
"books are paperbacks" is false, yet less than one percent
of mosquitoes carry the virus, while over eighty percent of books are
paperbacks. How are we to account for these puzzling facts?



It is clear that generics are not equivalent to universal statements,
but rather permit exceptions--that is, generics can be true even
if some (or sometimes many) members of the kind lack the property in
question. Generics also do not mean "most"; it is false
that most mosquitoes carry the West Nile virus and true that most
books are paperbacks, but our intuitions about the truth/falsity of
the corresponding generics are reversed.



As these examples suggest, *Gen* cannot be analyzed as sharing
a meaning with any of the standard quantifiers. One question that
comes up immediately is whether *Gen* can be considered a
quantifier in any sense. Carlson (1977) argued informally that it
could not, since generics do not tell us *how much* or *how
many*. He notes that, if asked "how many tigers are
striped", one could reply "most/all/many/some tigers are
striped", but not simply "tigers are striped" (see
Leslie (2007) for a more formal argument, which goes by way of the
premise that quantifiers exhibit isomorphism invariance, while
*Gen* does not.).



A significant number of theories concerning the meaning of generics
have been offered over the years. Most theories have focused primarily
on bare plural generics, though some theories are intended to cover
indefinite and definite singulars too. We will conclude with some
remarks concerning issues specific to indefinite and definite
singulars.


### 2.1 Possible Worlds and Normalcy-Based Approaches



Many accounts of generics are framed in terms of some or other type of
quantification over possible worlds (Dahl 1975, Delgrande 1987,
Schubert and Pelletier 1989, Asher and Morreau 1995, Krifka et al.
1995, Pelletier and Asher 1997, Greenberg 2003, and others). Often,
these possible worlds are employed to capture the intuition that
generics tell us something about what is *normal* for members
of a kind (see Nickel 2008, 2016). For example, it is natural to think
that a generic such as "tigers are striped" tells us
something about normal tigers; the only exceptions to it are those
tigers who are albino, and so, one could argue, in some respect
out-of-step with the norm for the kind. Similarly, "dogs have
four legs" may strike us as true because the only dogs that do
not have four legs either have birth defects or have met with
misfortune.



Possible worlds are helpful here, because they allow us to consider,
say, worlds in which things go *as normally as possible* for a
given tiger, even if life is *actually* quite abnormal for that
tiger. For example, Asher, Morreau, and Pelletier argue that
"*K*s Ph" is true iff for each individual
*K*, the most normal worlds for that *K* (according to a
contextually determined ordering base), are such that that *K*
Phs (Asher and Morreau 1995; Pelletier and Asher 1997). Glossed in
more intuitive terms, the account states that a generic
"*K*s Ph" is true iff each individual *K*
would have the property Ph if all were to go as normally as
possible for that *K* with respect to the relevant property.
Thus, while in actuality some dogs are three legged, one might suppose
that, *had things gone more normally for each of those dogs with
respect to how many legs they have*, they would have had four
legs.



Pelletier, Asher, and Morreau connect their semantic account of
generics to the literature on defeasible validity (McCarthy 1986;
Reiter 1987, and others). A set of premises defeasibly or
*non-monotonically* entails a conclusion if the conclusion is
likely or reasonable given the premises, yet it is nonetheless
possible for the premises to be true and the conclusion false. They
argue that there are many defeasibly valid patterns of entailment that
involve generics, and that their semantics explains why this is so.
For example, if Fido is a dog and dogs have four legs, then the
inference that Fido has four legs is held to be defeasibly valid. It
is *possible* that Fido is a three legged dog, but it is still
*reasonable* to suppose that Fido is four legged on the basis
of the premises. The reasonableness of this inference is explained on
Pelletier, Asher, and Morreau's semantics--the generic
"dogs have four legs" guarantees that, if things go
normally for a given dog with respect to its number of legs, then that
dog will have four legs. Since we have been given no reason to suppose
that Fido is abnormal, one may defeasibly conclude that Fido is four
legged.



Indisputably, a large number of true generics of the form
"*K*s Ph" are such that, if things go normally
for a given *K*, then it has the property Ph. However, there
would seem to also be a number of true generics which do not fit this
profile: "ducks lay eggs", "lions have manes",
"mosquitoes carry the West Nile virus", and "sharks
attack swimmers". The last two generics present a significant
difficulty for normalcy-based accounts, since it is surely not
*normal* for a mosquito to carry the virus, nor is it
*normal* for a shark to attack a bather. For generics such as
"ducks lay eggs" and "lions have manes",
several theorists have argued that the domain of discourse is
restricted so that we are talking about only the female ducks and the
male lions respectively, and thus have aimed to rescue normalcy-based
approaches from this criticism (e.g., Pelletier and Asher 1997), since
perhaps it is abnormal for a given female duck to fail to lay eggs.
Pelletier and Asher suggest that a generic can be restricted to a
subkind of the kind in question in this way; that is, "ducks lay
eggs" means *female ducks lay eggs* because *female
ducks* constitute a subkind of the kind *ducks*.



However, on such a proposal, it is difficult to avoid the prediction
that "ducks are female" should also be a true
generic--why can this generic not be made true by similarly
restricting the domain to include only this subkind of ducks? Or
conversely, consider "ducks don't lay eggs".
Certainly one subkind of ducks--namely the male
ducks--don't lay eggs, but this does not seem to suffice to
make the generic "ducks don't lay eggs"
true. Asher and Pelletier (2012) offer a development of the
normalcy-based account intended to remedy these problems.



Further, a recent experiment examined whether people think that a kind
in which a property is had only by one sex (i.e., where domain
restriction to a subkind is possible) is a better satisfier of the
generic than a kind in which half the members, regardless of sex, have
the property (i.e., where no such restriction to a subkind is
possible). If generics like "ducks lay eggs" are only
accepted because people are implicitly restricting the domain to a
subkind whose members generally possess the property, then they should
show a preference for one of the possible distributions over the
other. However, no such preference was found (Cimpian, Gelman and
Brandone 2010). Khemlani, Leslie, and Glucksberg (2012) also report
empirical evidence that further suggests that people do not understand
these generics to involve domain restriction--in particular, that
people are more likely to judge that an arbitrary duck lays eggs than
they are to judge that an arbitrary duck is female (but see
Lazaridou-Chatzigoga and Stockall (2013) for some evidence in favor of
domain restriction). This pattern is difficult to explain if people
only accept "ducks lay eggs" because of domain
restriction. If one cannot appeal to domain restriction to handle
"ducks lay eggs", then such generics would appear to
constitute counterexamples to this sort of approach.


### 2.2 Relevant Quantification and Situation Semantics



Appeals to domain restriction are not limited to normalcy-based
approaches. In light of generics such as "ducks lay eggs",
some theorists have argued that generics involve quantification over
*relevant* individuals (actual or possible), where context
determines which individuals are relevant (e.g., Schubert and
Pelletier 1987; Declerk 1991; Chierchia 1995). On such views, when we
consider a generic such as "ducks lay eggs", only the
mature, fertile female ducks enter into our evaluation of the
sentence, because, e.g., they are the only potential egg-layers. The
question that arises is how exactly to determine which individuals are
relevant. Schubert and Pelletier (1987) offer a detailed discussion of
how some of these restrictions arise--e.g., via presupposition,
focus, linguistic context, or explicit restriction as appropriate.



Ter Meulen (1986), Gerstner-Link (1988), and Cavedon and Glasbey
(1994) offer treatments of generics in the framework of situation
semantics (Barwise and Perry 1983). On such views, generics express
*constraints* on situations--e.g., "tigers are
striped" expresses the constraint that every situation involving
a tiger involves a striped tiger. Constraints are not reducible to the
properties of individuals (Cavedon and Glasbey 1994). The
interpretation of a generic on these views is relative to a given
context (or "channel" as they style it), so as on the
above views, generics such as "ducks lay eggs" are
evaluated only with respect to the female ducks (Cavedon and Glasbey
1994).



As noted above, there are philosophical and empirical difficulties
(Cimpian, Gelman et al. 2010; Leslie 2008; Khemlani et al. 2012)
facing any accounts that rely on domain restriction to handle generics
such as "ducks lay eggs". For these accounts to succeed,
these difficulties would need to be addressed in more detail.


### 2.3 The Indexical Approach



Sterken (2015a) has recently argued that relevant quantification alone
cannot capture the extent to which generics are context-sensitive.
According to Sterken, not only does lexical restriction vary as a
function of context, but so does quantificational force. As an
illustration, consider the generic "cats are black". This
could be uttered by parents trying to teach their children about cats,
or it could be uttered in response to a teacher asking the class what
colors cats are. In the first context, the truth of "cats are
black" seems to require that all cats be black. In the second
context, the truth of "cats are black" seems to require
only that some cats are black.



Sterken argues that the best explanation of why the truth conditions
of generics vary across context in this way and others is that
*Gen* is an indexical. In terms of logical form, this means
that *Gen* is composed of two free variables: one representing
quantificational force and one representing lexical restriction. Like
all indexicals, *Gen* has what Kaplan (1989) calls a
*character*, a function from contexts of utterance to the
semantic values. Given a context of utterance, the character of
*Gen* assigns semantic values to the free variables, resulting
in the generic expression having as its content a particular
generalization. The resulting view is intended to capture the various
ways the truth conditions of a generic depend not only on the kind in
question and the property being predicated, but also on the wider
context of utterance.



The main challenge for the indexical approach is that of specifying
the character of *Gen*. Sterken suggests that the character of
*Gen* is such that the content of a generic utterance depends
on what generalization the speaker intends the utterance to express
and whether her intention could be recognized by a sufficiently
idealized person that is privy to the conversation. If the character
of *Gen* is as described, this seems to explain why generics
can be so flexible. However, it also seems to make generics
*too* flexible: some generics (e.g., "tigers don't
have stripes", "ravens are white") seem
straightforwardly false and some generics seem straightforwardly true
(e.g., "triangles have three sides", "primates
aren't avians"), regardless of the speaker's
intentions (and of anyone's ability to detect those intentions).
Whether such an account can handle such cases remains to be seen.
Moreover, the indexical account is supplemented by Sterken with an
error theory for generics such as "mosquitoes carry West Nile
virus" (2015b), further increasing its flexibility. For critical
discussion of the motivation for the error theory, see Almotahari
(forthcoming). More generally, the indexical account--unless it
is supplemented with a rich metasemantic account of the character of
*Gen*--is not clearly constrained enough to issue in
substantive predictions concerning the truth/falsity of generics.


### 2.4 Stereotypes and Prototypes



A somewhat different approach to the semantics of generics is taken by
theorists who suppose that generics express stereotypes or prototypes.
On such views, "tigers are striped" would express that the
stereotypical or prototypical tiger is striped, and likewise,
"sharks attack bathers" would express a belief about the
stereotypical or prototypical shark. Geurts (1985) and Declerk (1986)
suggest that generics may be interpreted as expressing culturally
accepted stereotypes, and Platteau (1980), Nunberg and Pan (1975), and
Heyer (1985, 1990) claim that generics express prototypes, in the
sense of Rosch (1978). Thus on such views, "tigers are
striped" would express the fact that the stereotypical or
prototypical tiger is striped.



A general concern with views of this type is that they would seem to
make the holding of the relevant sort of false belief sufficient to
render the generic true. For example, suppose that people falsely
associate sliminess with snakes in the relevant way (e.g., as a
culturally held stereotype, or part of the Roschean prototype, etc).
This does not make the generic "snakes are slimy" true
(Krifka et al. 1995). While it is plausible that people often
*assert* generics on the basis of their
prototypical/stereotypical beliefs, it is implausible to think that
these beliefs enter into the *truth conditions* of generics.
Stereotypical beliefs can be, and often are, false.


### 2.5 Probabilitistic Approaches



Cohen (1996, 1999, 2004) argues that generics can be understood in
terms of comparative probabilities. There are two different ways for a
generic to be true on Cohen's view. The first way (Absolute) can
be illustrated by "tigers are striped". This is a true
generic because (roughly speaking) a randomly chosen tiger is more
likely than not to be striped. The second way (Relative) a generic can
be true involves comparison with other kinds. For example, on
Cohen's account, "mosquitoes carry the West Nile
virus" is true because (again roughly speaking) if we pick a
mosquito and another insect at random, the mosquito is more likely
than the insect to carry the West Nile virus. Thus on Cohen's
view, generics are made true (or false) by such probabilistic
considerations. More precisely, Cohen's categories are as
follows:



**Absolute generics**
  

"*K*s are *F*" is true iff the probability
that an arbitrary *K* that satisfies some predicate in
Alt(*F*) satisfies "is *F*" is greater than
.5.



**Relative Generics**
  

"*K*s are *F*" is true iff the probability
that an arbitrary *K* that satisfies some predicate in
Alt(*F*) satisfies "is *F*" is greater than
the probability that an arbitrary member of Alt(*K*) that
satisfies some predicate in Alt(*F*) satisfies "is
*F*".



(In the above, Alt(*F*) is the set of contextually relevant
alternatives to the property in question, and Alt(*K*) is the
set of contextually relevant alternative kinds to the kind in
question.) As it stands, however, Cohen's account incorrectly
predicts that generics such as "bees are sterile" will be
true, since the probability that a given bee is sterile is greater
than .5. To deal with such cases, Cohen introduces the homogeneity
constraint:



**Homogeneity Constraint**
  

The above probability conditions (exceeding .5, or exceeding that of
the arbitrary alternative to the kind) should hold in *all salient
partitions* of the kind.



Generics such as "bees are sterile" are now predicted to
be false, because there is a salient partition of bees into workers,
queens, and drones, and queen bees have a very low probability of
being sterile.



However, Cohen's account may face some counterexamples. For
example, humans are more likely to suffer from autism than other
mammals, and so "humans are autistic" would seem to be
falsely predicted to be a true (relative) generic, and it is hard to
see how homogeneity could undermine this prediction (Leslie 2008).
This example illustrates that unique possession of a property by a
kind is not generally sufficient for the truth of a generic, yet the
category of relative generic predicts that, modulo homogeneity, this
should suffice.



Conversely, consider "mosquitoes carry West Nile virus".
This is a true relative generic on Cohen's view. However,
suppose that fleas also carried the virus, and did so at a somewhat
higher rate than mosquitoes. Suppose further that the flea population
swelled to immense proportions, so that fleas outnumbered all other
insects. As the flea population increases, there will come a point at
which mosquitoes cease to be more likely than the arbitrary insect to
carry West Nile virus, and so the generic "mosquitoes carry West
Nile virus" would be predicted to become false. It is perhaps
natural to think, though, that these are circumstances under which
"mosquitoes carry West Nile virus" would remain
true--after all, one could still catch the virus from a mosquito!
If this is correct, then it suggests that the analysis in terms of
relative probability may not be correct (Leslie 2008).



Empirical work also suggests that the homogeneity constraint does not
guide people's understanding of generics. For example, Cimpian,
Gelman, and Brandone (2010) found that adults are not at all reluctant
to accept a generic that involves a property found only in one salient
partition of a kind, *contra* the predictions of the
homogeneity constraint (though this was not the intent behind the
experiment).



Nickel (2012) offers a different kind of counterexample to
Cohen's account: cases involving *polarization*. To
illustrate, Nickel asks us to consider a case in which some Dutch
sailors are among the best in the world. Moreover, the proportion of
Dutch sailors who meet this high standard exceeds the proportion of
German sailors and the proportion of French sailors who meet it.
Nevertheless, suppose that most Dutch sailors are very poor sailors.
Intuitively, the generic "Dutchmen are good sailors" seems
false in this case. But Cohen's account implies that it is true,
for the probability that a Dutchmen is a good sailor is higher than
the probability that someone from a relevant alternative country is a
good sailor, and the homogeneity constraint is satisfied.


## 3. Indefinite, Definite, and Bare Singular Generics



The above discussion was primarily centered on accounts of bare plural
generics, which have received the most discussion in the literature.
Singular generics introduce their own sets of complications.


### 3.1 Indefinite Singular Generics and Normativity



Unlike bare plurals, singular generics can easily be infelicitous. For
example, it is perfectly fine to say
 (36)
 or
 (37):



(36)
A madrigal is polyphonic
(37)
A football hero is popular


But not
 (38):



(38)
\*A madrigal is popular


(Notice, however, that the plural version of
 (38)
 "madrigals are popular" is perfectly felicitous (though
perhaps false, unfortunately).)



Lawler (1973) notes that indefinite singulars are only felicitous when
they express properties that are somehow "necessary",
"essential" or "inherent" to the kind.
Burton-Roberts (1977) argues that indefinite singulars carry a special
normative force, while Krifka et al. (1995) take a different tact,
arguing that the facts can be accounted for in terms of logical
form.



More generally, linguists such as Carlson (1995), Cohen (2001), and
Greenberg (2003) have noted that generics can sometimes have a
normative flavor, e.g. "a gentleman opens the door for
ladies" or "boys don't cry." A connection
between linguistic form (e.g., bare plural vs. indefinitely singular)
and normativity is often drawn, with some theorists such as Greenberg
(2003) and Cohen (2001) arguing that indefinite singulars can express
only "rules and regulations", in the sense of Carlson
(1995).



Greenberg and Cohen offer distinct semantic analyses of the phenomenon
of normative generics: Greenberg (2003) implements her analysis by way
of possible worlds semantics, while Cohen proposes that the logical
form of such normative generics are entirely different from that of
descriptive generics. In particular, for Cohen (2001), normative
generics assert that certain rules are in effect, as opposed to
expressing generalizations over kinds.



Leslie (2015b) offers an alternative account of how some generics can
have normative force, building on the work of Knobe, Prasada, and
Newman (2013) on dual character concepts. Knobe et al. note that
certain concepts seem to have dual normative/descriptive senses. For
example, we might say of a professional scientist who cares only about
getting grants and publications and not at all about discovering the
truth that *though there is a sense in which they are clearly a
scientist, there is also a sense in which they are not a (true)
scientist*. Conversely, we might say of a postal worker who
applies the scientific method whenever they can and who cares about
truth above all else that *even though there is a sense in which
they are clearly not a scientist, there is nonetheless a sense in
which they are a (true) scientist*. Leslie proposes that a given
generic has normative reading just in case the kind in question is
associated with a dual character concept.



Unlike Greenberg, Cohen, and Leslie, Hesni (2021) argues that the
normative force of generic statements cannot be located in the
semantics of generic statements. Instead, Hesni proposes that when we
consider a wider variety of generic sentences that do not contain dual
character concepts but appear to have normative force in certain
contexts (e.g., "Rocks aren't breakfast"), we must
appeal to Gricean pragmatics to explain their normative force.


### 3.2 Definite and Bare Singular Generics



Definite singular generics appear to invoke constraints similar to
those of indefinite singulars, but also some more besides. For
example, definite singular subjects are often infelicitous if they do
not refer to well-established kinds (Krifka et al. 1995; example from
Carlson 1977, attributed to Barbara Partee):



(39)
The coke bottle has a narrow neck
(40)
\*The green bottle has a narrow neck


What does it take to be a well-established kind? Krifka et al. suggest
that almost anything can become a well-established kind given an
appropriate body of background knowledge. For example, suppose it is
well known that green bottles preserve the effectiveness of certain
life-saving antibiotics. In this context, a definite singular generic
like "The green bottle saves lives" might be true.



Other constraints on the acceptability of definite singulars have been
noted by Nunberg and Pan (1975), Carlson (1977), Dahl (1985), and
others. However, definite singular generics have received less
attention overall than indefinite singulars, while bare plurals have
received by far the most discussion in the literature.



In addition to definite and indefinite singular generics, there are
also bare singular generics, which feature mass nouns in the subject
position (Ojeda 1991; Heyer 1987; Back 1996, Carlson 2011;
Wilkinson 1995). For example, "Gold is a metal" and
"Nicotine is highly addictive" are two true bare singular
generics. Like definite singular generics, bare singular generics have
received less attention than definite singular generics and bare
plural generics.


## 4. Generics and Psychology



In recent years, there has been increasing interest in generic
generalizations among psychologists. Cognitive psychology has long
been interested in understanding how our conceptual knowledge
concerning kinds is organized and represented; however, until somewhat
recently the connection with generic sentences, and the
generalizations they articulate, had not been explored.
Psychologists' interest in generics lies primarily with what
these sentences can reveal about our basic ways of conceiving of
kinds, rather than specifically with formulating a semantic analysis
of *Gen*. However, several results from psychology arguably
place important constraints on what the semantics of generic sentences
might look like.


### 4.1 The Generics-as-Defaults Hypothesis



Infants are able to make generalizations concerning kinds and
categories in their first year of life (e.g., Baldwin, Markman, and
Melartin 1993), and by the mid-preschool years, children hold richly
structured and detailed beliefs about the general properties of
members of kinds (e.g., Gelman 2003). An important question in
cognitive development concerns the nature of these generalizations.
How might we characterize these cognitively fundamental
generalizations? To what sorts of information is our most basic way of
generalizing sensitive? And how might these generalizations be
articulated in natural language, once it is acquired?



Several researchers have proposed that generic sentences articulate
cognitively fundamental, default generalizations, and that quantified
statements, in contrast, articulate cognitively more sophisticated
ones (e.g., Cimpian and Erickson 2012; Gelman 2010; Leslie 2007, 2008,
2012). Generics are acquired early in development, by approximately 30
months of age (Gelman, Goetz, Sarnecka and Flukes 2008; Gelman and
Raman 2003; Graham, Nayer and Gelman 2010). By 30 months, children
understand that generics tolerate exceptions (Gelman and Raman 2003),
and several studies have found that children's judgments of
generics are similar to adults' judgments throughout the
preschool years (e.g., Brandone, Cimpian, Leslie and Gelman 2012;
Brandone, Gelman, Hedglen 2015; Hollander, Gelman and Star 2002).
Interestingly, preschool children, like adults, understand that, e.g.,
"birds lay eggs" can be true yet "birds are
girls" false, even though only "girl" birds lay
eggs. Thus even preschoolers understand at least some of the
"troublesome" generics--the generics that cause
difficulties for the standard semantic analyses of generics--in
the same way that adults do.



Interestingly, several studies have found that, throughout the
preschool years, children have a tendency to interpret kind-wide
quantified statements as generics--e.g., evaluating a statement
quantified with "all", "most" or
"some" as though it were a generic. This phenomenon has
been documented among English-, Mandarin-, and Quechua-speaking
children (Brandone et al. 2015; Hollander et al. 2002; Leslie and
Gelman 2012; Mannheim et al. 2011; Tardif et al. 2010; see also Gelman
and Tardif 1998 for more discussion of the acquisition of generics by
Mandarin-speaking children). The tendency is not limited to children
either; under some circumstances, adults will also
"default" to the generic interpretation when confronted
with a quantified statement. For example, adults show a consistent
tendency to accept, e.g., "all ducks lay eggs", despite
knowing that male ducks don't lay eggs (a tendency which does
not seem to be due to adults interpreting the quantified statement as
ranging over subkinds of ducks; Leslie, Khemlani and Glucksberg 2011;
Meyer, Gelman and Stilwell 2011; but see Lazaridou-Chatzigoga, Katsos,
and Stockall 2015). Further, a range of adult reasoning errors with
universal quantifiers are readily explicable on the hypothesis that
adults sometimes interpret universally quantified statements as
generics (Jonsson and Hampton 2006; Sloman 1993, 1998).
Additionally, both adults and preschoolers frequently recall
quantified statements as generics, but not *vice versa*, a
tendency that has been documented in both Spanish and English (Gelman,
Sanchez Tapia, and Leslie 2015; Leslie and Gelman 2012).



If generics do indeed give voice to cognitively fundamental, default
generalizations, this would explain an otherwise puzzling fact: the
absence of an articulated word "gen" in most or perhaps
even all natural languages. That is, languages rarely if ever contain
a dedicated, articulated operator that uniquely signals a generic
statement, in the way that "all" signals a universal
statement. Rather, languages overwhelmingly exploit less marked
syntactic forms to express generic statements (Dahl 1985; Krifka et
al. 1995; see also Carlson 2012). If generics express default
generalizations, this pattern can be explained: in general, if a
system has a default way of operating, then it is inefficient to
explicitly instruct the system to operate in this way, since it will
do so anyway, even in the absence of instruction. If processing a
universal statement requires the cognitive system to *deviate*
from its default way of generalizing, then explicit instruction is
required--hence the word "all". If generics require
no such deviation, then languages need not contain a word
"gen" (Leslie 2008).



The empirical findings suggest that these cognitively fundamental
generalizations are articulated as generics rather than quantified
statements. Compared to generic generalizations, quantified
generalizations represent cognitively more taxing and sophisticated
generalizations. This is potentially of philosophical interest since
many of the semantic analyses of *Gen* reviewed above aim in
some way or other to reduce *Gen* to the more theoretically
tractable quantifiers--for example, the possible worlds and
normalcy-based approaches often analyze *Gen* in terms of
universal quantification over worlds, individuals, or both. Thus, on
such an account, generic generalizations constitute a specific kind of
universal quantification--the restriction of universal
quantification to a range of (often complex, abstract) entities. On
such an account, generics depend on universal quantification, and the
latter is in some sense more fundamental than the former. Depending on
one's view of the subject matter of semantics, it may be a
challenge to reconcile such a view with the available psychological
data.


### 4.2 Are Generics Sensitive to Content-Based Factors?



Researchers who take a psychological approach to generics have also
recently proposed that our judgments of generics may be sensitive to a
range of content-based factors. That is, while standard semantic
analyses of generics aim to treat them in an abstract, formal
framework, psychologically-oriented theorists have argued instead that
generic generalizations are sensitive to the nature of the property
being generalized. For example, consider the generics
"mosquitoes carry West Nile virus", "sharks attack
swimmers", and "ticks carry Lyme disease". People
robustly accept such generics, despite knowing that very few members
of the kind have the property in question. One possibility is that
such familiar generics are accepted at low prevalence levels because
the property in question is dangerous--the sort of property one
would do well to avoid (Leslie 2008). This hypothesis is
supported by experimental data that finds that people are more likely
to accept *novel* generics at low prevalence levels if the
property in question is a dangerous one (Cimpian, Brandone and Gelman
2010). As noted above, generics like "ticks carry Lyme
disease" have proved difficult for the formal semantic
approaches to accommodate. If generics are indeed sensitive to factors
such as whether the property is question is dangerous or not, this
difficulty would be expected--since formal semantic frameworks do
not normally take into account such features of the property, but
rather aim to abstract away from such content-based
considerations.



If generic generalizations are indeed sensitive to the nature of the
property being generalized, might that account for other
"troublesome" generics? In addition to being sensitive to
whether the property is dangerous or not, it has been proposed that
generics may also be sensitive to whether the property in question is
characteristic of the kind (Cimpian, Brandone et al. 2010; Cimpian,
Gelman et al. 2010; Gelman and Bloom 2007; Leslie 2007, 2008; Prasada
and Dillingham 2006, 2009). Examples of characteristic properties of
kinds would include salient, distinctive physical features (e.g.,
"lions have manes"), methods of reproduction for animal
kinds (e.g., "ducks lay eggs"), and functions for artifact
kinds (e.g., "Orange-Crusher-2000s crush oranges"). If a
generic attributes a characteristic property to the kind, then the
generic may be accepted even if few members of the kind have the
property in question.



If generics are indeed sensitive to such factors, it may be possible
to explain why some generics are accepted even though the property is
not prevalent among members of the kind. What, though, of generics
such as "books are paperbacks" or "school teachers
are female"? People tend to reject such generics, despite
judging that the property in question is highly prevalent (Prasada et
al. 2013). One proposal is that generics may be sensitive to the
nature of the *exceptions* to the generic claim (Leslie 2007,
2008). That is, amongst the members of the kind that fail to have the
predicated property, it may matter *how* they fail to have the
property--in particular whether they simply lack the property, or
whether they have an equally salient, concrete, positive property
*instead*. The non-infected ticks simply *do not carry Lyme
disease*--they do not have an alternative property instead.
However, the books that are not paperbacks are instead hardcover.
Similarly, people who are not right-handed are instead
*left-handed*; elementary school teachers who are not female
are *male*. Intuitively, one might feel as though one would be
"overlooking" these hardcover books, these left-handed
individuals, and these male school teachers if one accepted the
generics in question. Thus, it is possible that generics may be
sensitive to the nature of the exceptions to the generalization.
However, more empirical investigation is needed on this point.


### 4.3 A Bayesian Model of Generics



Tessler and Goodman (2019) offer an account of generics that is rooted
in a Bayesian computational approach to cognition. They model
acceptance/rejection of a generic as a speaker's decision to
produce an utterance of the generic to a naive listener. The goal of
the speaker, on their model, is to produce an utterance that aligns
the listener's beliefs about the prevalence of the property
among members of the kind (the "referent prevalence" in
their terminology) with the speaker's beliefs. The
speaker's decision is driven by whether the referent prevalence
is more likely under the listener's prior beliefs vs. their
posterior beliefs after hearing the generic. On their model, generics
have a threshold semantics, according to which a generic is true if
the referent prevalence exceeds a threshold, however this threshold is
unspecified and unknown by both speaker and hearer. Bayesian
computational modeling provides a mathematical framework in which such
uncertainty can be readily handled; specifically, interpretation on
the model involves integrating over the possible values of this
threshold. A listener's posterior beliefs are arrived at by
Bayesian updating, such that they are proportional to the product of
the listener's prior beliefs about the distribution of the
prevalence \(p\) of the property in question (i.e., over comparable
kinds), \(Pr(p),\) the probability of possible thresholds \(\theta\),
\(Pr(\theta),\) and a delta function that is 1 if \(p \gt \theta\) and
0 otherwise.



To put the model in less precise but more intuitive terms, the
decision to utter a generic "\(K\)s are \(F\)" depends on
beliefs a naive listener would likely have concerning the distribution
of the property \(F\) over comparable kinds. Consider, for example,
the distribution of the property *laying eggs* over animal
kinds. For most animal kinds, the proportion that lay eggs is
approximately zero, but there are some animal kinds for which ~50% of
members lay eggs. Any other proportions of egg-laying are quite
unusual. This describes the shape of the prevalence prior for
*laying eggs*. Consider, then, an utterance of the generic
"robins lay eggs": approximately 50% of robins lay eggs,
and hearing such a generic will, according to the mathematics of the
model, lead the naive listener to update their prevalence prior in
such a way that most of the probability distribution will be clustered
around 50% and very little will remain around 0%. Thus, uttering this
generic will lead the listener's prevalence posterior to be
better aligned with the speaker's beliefs than their prevalence
prior, and so the generic is endorsed.



Tessler and Goodman's model does a remarkable job of predicting
the degree to which people endorse a given generic with great
quantitative accuracy, and it extends a growing body of evidence in
cognitive science that much of human cognition, including early
cognitive development, involves or approximates to Bayesian inference
(e.g., for a recent review, see Ullman and Tenenbaum 2020). While
their model predicts that prior beliefs about the distribution of the
prevalence of the property over comparable kinds mediates all
endorsement/rejection of generics, they allow that these priors may be
influenced by content-based factors. For example, "mosquitoes
carry West Nile virus" is predicted to be accepted with a high
degree of confidence by the model because the prevalence prior for
*carrying West Nile virus* is almost entirely bunched up very
close to zero, and correspondingly the prevalence posterior upon
hearing the generic shifts modestly over to low but decidedly non-zero
values. If people have a higher order prior expectation that
strikingly dangerous properties are rare, such that the prevalence
priors for such properties resemble that of *carrying West Nile
virus*, then this would mean that people would be disposed to
accept generics that predicate such properties, even though the
referent prevalence is low.


### 4.4 Inferences from Generics



Despite the fact that people are often willing to accept generics
despite knowing that only a minority of the kind has the property
(e.g., Brandone et al. 2012; Cimpian, Brandone et al. 2010), the
available data suggest that people are nonetheless disposed to treat
generics as quite inferentially powerful. For example, if people are
told that a given percentage of a novel animal kind has a property,
they are often willing to accept the corresponding generic at
prevalence levels of 50%, 30%, or even 10%, particularly if the
property being described is dangerous and/or characteristic of the
kind. However, if people are instead presented with the generic and
asked to estimate the prevalence of the property, the estimates are
very high indeed--often reaching 100% (Cimpian, Brandone et al.
2010). Preschool-aged children show a similar pattern (Brandone et al.
2015).



These studies show that people give very high estimates of prevalence
when presented with a generic statement concerning a novel animal
kind. When the generics concern familiar kinds, prevalence estimates
can be more realistic. Nevertheless, accepting a generic increases
people's tendency to believe a given member of the kind will
have the property in question, over and above their beliefs about the
prevalence of the property (Khemlani, Leslie, and Glucksberg 2012).
For example, people correctly give comparable prevalence estimates
concerning the number of ducks that are female vs. lay eggs. However,
when asked to judge whether a given duck would have a property (e.g.,
"suppose you are told that Quacky is a duck. Evaluate the
following statement: Quacky lays eggs"), people were
significantly more likely to agree that the duck would lay eggs than
they were that the duck would be female (Khemlani et al. 2012). These
results suggest that people may treat generics as being inferentially
quite powerful, in a way that cannot be reduced to their background
beliefs about the prevalence of the property. When people are asked to
judge whether a given member of a kind will have a property or not,
they rely in part on their background judgment of the generic, rather
than solely on their beliefs about how prevalent the property is.



These findings support the idea that accepting a generic disposes
people--all else being equal--to believe that an arbitrary
instance of the kind will have the property, as has long been
suggested in the defeasible reasoning literature (e.g., Pelletier and
Asher 1997). However, the defeasible reasoning literature has tended
to focus on "non-troublesome", high prevalence generics
like "tigers are striped"; it is notable that people show
a tendency to draw such inferences even for lower prevalence
generics.


## 5. Beyond Language: Philosophical Applications of Generics



The study of generics is not only of interest from the perspective of
understanding language, or the psychology associated with that portion
of language. In recent years, there has been an upsurge of interest in
the applications of generics. The range of potential applications of
generics has proved extremely broad, and comprises issues from social
prejudice to the sorites paradox and the principle of sufficient
reason.


### 5.1 Generics, Stereotyping and Prejudice



From a young age, we conceive of certain kinds, both natural and
social, as having a fundamental, underlying nature that is shared by
its members (e.g., Gelman 2003). That is, we believe that, while some
kinds may group individuals together on the basis of superficial
properties (as an extreme example, consider the kind
*trinkets*), other kinds group their members together on the
basis of deep, intrinsic similarities (animal kinds are paradigmatic
examples here). Kinds that fall in the latter category are said to be
*essentialized* in the psychological sense. Members of an
essentialized kind are believed to be deeply similar to each
other--even if they seem to differ superficially--and are
believed to share a range of important properties, which are the
causal upshot of their shared natures (Gelman 2003). In the social
realm, essentialist beliefs can be very damaging, and the groups that
are most highly essentialized often face the worst forms of social
prejudice (Haslam, Rothschild and Ernst 2000, 2002).



Sally Haslanger (2011) offers a fascinating analysis of generics that
concern social kinds, for example "women are submissive"
(see also McConnell-Ginet 2012 and Leslie 2014 for related
discussion). It may be a fact that, given social circumstances, the
majority of women defer to men on important decisions and life
choices. With some complications (as noted above), this sort of high
prevalence often suffices for a generic to count as true (e.g.,
Prasada and Dillingham 2006, 2009). Haslanger poses the question: even
if we are in the circumstances that would plausibly render the generic
true, might there still be something objectionable about uttering the
generic? She argues that indeed there is, if the generic makes
reference to an essentialized social kind and thereby perpetuates
various forms of oppression. Generics, Haslanger argues, suggest that
the property is grounded in the nature of the kind, and so an
utterance of "women are submissive" invites the
interpretation that it lies in the very nature of women to be
submissive--rather than their submissiveness coming about as the
result of extrinsic, accidental, and changeable social
circumstances.



Empirical evidence supports Haslanger's hypothesis. For example,
from a young age, we tend to interpret information conveyed via
generic language as indicating a stable and intrinsic property of the
kind, whether the kind is natural or social (e.g., Cimpian and
Erickson 2012; Cimpian and Markman 2009, 2011). Further, hearing
generic language about a novel social or animal kind leads both
children and adults to essentialize that kind in the first place . For
example, even a wholly novel social group, composed of individuals who
are diverse for race, ethnicity, gender, and age will rapidly be
essentialized by preschoolers and adults alike if they hear various
properties being attributed to the group via generic language (Gelman,
Ware and Kleinberg 2010; Rhodes, Leslie and Tworek 2012; Leshin,
Leslie and Rhodes 2021). (An interesting quandary emerges when we note
that quantified statements are often interpreted and recalled as
generics: is there any way to speak of social groups at a general
level without inducing essentialist beliefs?)



As another illustration of the impact generic language, and language
about identity categories more generally, can have on young children,
Rhodes and Leslie noted that science is often described to young
children using identity-focused language, e.g., "Let's be
scientists! Scientist explore the world using their senses."
However, action-focused language offers an alternative way to
communciate much the same content, e.g., "Let's do
science! Doing science means exploring the world with our
senses." In a series of experiments, Rhodes and Leslie and
collaborators have found that children who belong to social groups
that are underrepresented in science (girls, children from
underrepresented minorities or lower income backgrounds) show more
engagement and persistence when they hear science described using
action-focused language as opposed to identity-focused language (e.g.,
Rhodes, Cardarelli and Leslie 2020).



In addition to fostering essentialist beliefs, generics are also often
used to communicate normative statements about social groups, e.g.,
"boys don't cry", "a woman puts family before
career", "friends don't let friends drive
drunk" (see also section 3.2 above). Generics such as these are
not intended as descriptions of the facts on the ground, but rather
carry a particular normative force; "friends don't let
friends drive drunk" was not introduced as a banal observation
about what is in fact the case, but rather was introduced precisely to
address the fact that, all too often, people were allowing their
friends to drive under the influence. In the context of gender, these
normative generics can serve as a concise (and child-friendly) means
of communicating and sustaining problematic social norms. Moreover,
recent empirical work reflects that very young children may interpret
generics as having prescriptive force, even if those generics seems to
adults to be only descriptive generalizations (Roberts, Ho and Gelman
2017).



Generic generalizations may be relevant to understanding social
prejudice in other respects too. For example, "ticks carry Lyme
disease" is accepted at low prevalence levels, perhaps because
carrying Lyme disease is a dangerous property, of the sort one would
wish to avoid. What then are we to make of similar generics in the
social realm, e.g., "Muslims are terrorists"? Clearly,
there is something deeply wrong with the latter that is not wrong with
the former. One possibility is that these "dangerous
generics" involve the assumption that the members of the kind in
question share a nature that ground the property in question (or at
least the corresponding disposition or propensity), and so
generalizations such as "Muslims are terrorists" again
involve false essentialist beliefs about social groups (Leslie
2017).



As a final illustration of the significance of generics for the social
world, consider the phenomenon of stereotype threat (Steele and
Aronson 1995; Steele 2010). Stereotype threat occurs when members of a
stigmatized social group perform worse than they otherwise would have,
because their membership in that group was made salient to them. For
example, the performance of women and African-Americans on
standardized tests is lowered if they are reminded first of their
group membership by, e.g., being asked to report their gender or race
before the exam. Interestingly, stereotype threat on a totally novel
task can be induced by simply uttering a generic--e.g., telling a
girl "boys are really good at this game" (Cimpian 2013;
Cimpian, Mu and Erickson 2012). Simply hearing an evaluative generic
statement about a gender group was enough to impair children's
performance.



These findings suggest that generic language has an undesirable
influence on how we come to understand the social world around us.
Nevertheless, Ritchie (2019) defends the use of some social generics
(e.g., "Blacks face economic, legal, and social
discrimination", "Women are expected to want
children") on the grounds that they are uniquely apt for
describing and ameliorating conditions of structural injustice.


### 5.2 Generics and Philosophy More Generally



Some philosophers have recently applied the study of generics to a
range of long-standing philosophical issues and puzzles. As a
fascinating illustration, Roy Sorensen (2012) argues that a proper
understanding of generics can solve the sorites paradox. An example of
the sorites paradox is the following: *1 is a small number; small
numbers have small successors; therefore 1,000,000,000 is a small
number*. The second premise is the inductive step, and is here
formulated as a generic. Sorensen proposes that, like most generics,
the inductive step admits of exceptions: there are some (or at least
one) small numbers whose successor is not itself a small number. If
this is so, then the paradox is resolved: the argument is simply
invalid. In order for the argument to be valid, the inductive step
cannot be an exception-tolerating generic, but rather an exceptionless
universal, e.g., *for all *n*, if *n* is a small
number, so is \(n+1\)*. Indeed, the paradox is often formulated in
this way--i.e., with a universal as the inductive step. Here,
however, Sorensen argues that we are simply interpreting the universal
as a generic, just as when adults accept "all ducks lay
eggs" despite knowing that male ducks do not lay eggs (Leslie et
al. 2011).



A similar strategy is applied by Mahrad Almotahari (2022) to the
*kalam* cosmological argument: *Everything that begins
to exist has a cause for its existence; the universe began to exist;
therefore the universe has a cause for its existence.* Almotahari
argues that acceptance of the first premise of the argument rests on
the generic overgeneralization effect. Certainly, anything that we
encounter in ordinary life that begins to exist has a cause, and it is
entirely reasonable to accept the corresponding generic *things
that begin to exist have causes for their existence.* But the
*kalam* cosmological argument requires a universal
generalization, not a generic one, and Almotahari argues that this is
a step to which we are not entitled.



Additionally, generics have been said to solve, or at least
illuminate, other long-standing philosophical puzzles. For example,
Kai Yuan Cheng (2011) argues that a proper understanding of generics
and habituals can help resolve the Kripke/Wittgenstein rule-following
paradox. Bernhard Nickel (2010, 2014) has argued that generics can be
used to analyze *ceteris paribus* laws; similarly, Asher and
Daniel Bonevac (1996, 1997) have relied on a normalcy-based approach
to generics to provide an account of *prima facie* obligation.
Michael Graff Fara (2005) and Ryan Wasserman (2011) both recruit
generics and habituals to give accounts of dispositions.



Reflection on generics has also influenced debates about philosophical
methodology. Mark Johnston (2016) suggests that certain well-known
inadequacies of the "method of cases" in the philosophy of
personal identity can be explained by the fact that we as philosophers
have treated what is in fact merely generic-based--and thus
exception-tolerating--knowledge of the application conditions of
our concepts as if it were knowledge of universal necessary and
sufficient conditions for the application of the relevant concepts.
Johnston and Leslie (2012, 2019) rely on similar considerations to
question the philosophical methodology known as the Canberra Plan.
Lastly, Lerner and Leslie (2013) argue that a greater understanding of
the role of generics in moral cognition undermines certain
applications of the method of reflective equilibrium within normative
ethics.