## 1. Formulating Haecceitism



Haecceitism is a modal thesis. Like other modal theses, there are
competing metaphysical frameworks in which it might be expressed. Some
of these frameworks involve a commitment to possible worlds or maximal
possibilities, while other frameworks aim to do without these
commitments. To further complicate matters, some frameworks
distinguish possible worlds from the maximal possibilities they
represent while other frameworks collapse this putative
distinction by identifying maximal possibilities with possible worlds.
This section surveys some of the options for formulating and
interpreting haecceitism but, as Skow (2008, 2011) argues, any
formulation of haecceitism that employs the framework of possible
worlds will tendentiously presuppose something about the nature of
possibilities or possible worlds. For this reason, the proper
formulation of haecceitism is itself a matter of controversy.


### 1.1 Possibilities and Possible Worlds



For modalists, the correct analysis of modality involves no
quantification over possibilities or possible worlds. (On modalism,
see Forbes (1992), Melia (2003: 81-98) and Peacocke (1999:
155-159).) Instead, modal notions are properly understood in
terms of primitive modal operators like the box and diamond of modal
logic. Since modalists do without quantification over possibilities or
possible worlds, haecceitism and anti-haecceitism cannot be expressed
in terms of differences between such entities. But, following Skow
(2008), the modalist can nevertheless characterize anti-haecceitism as
follows:



**Modalist** **Anti-Haecceitism**:
Necessarily, the world could not be non-qualitatively different
without being qualitatively different.



Within the modalist framework, haecceitism is therefore equivalent to
the denial of Modalist Anti-Haecceitism.



Those who reject the expressive limitations of modalism can help
themselves to richer ontological resources in characterizing
haecceitism. For example, if quantification over possibilities is
permitted, two distinctions among possibilities prove especially
useful for formulating haecceitism. According to the first
distinction, some possibilities are *maximal*: they are total
ways the entire world could have been. So, for any possibility, a
maximal possibility includes that possibility or its negation. (On
some views, talk of possibilities including other possibilities is
understood in terms of entailment. On other views,
"inclusion" is understood in terms of set
membership--e.g., membership relations between sets of
propositions. Here, inclusion is taken as a neutral bit of
terminology.) In contrast, *non-maximal* possibilities like the
possibility that Obama is human are less than total ways things could
have been.



A second distinction among possibilities divides *non-qualitative
possibilities*, which are ways specific individuals like Napoleon
or Nefertiti could have been, from *qualitative possibilities*,
which are not tied to any specific individuals. So, for example, the
possibility that Napoleon escapes Elba is non-qualitative, while the
possibility that there are four red objects is a qualitative
possibility. (On some views, the distinction between qualitative and
non-qualitative possibilities can be identified with or analyzed in
terms of the distinction between *de dicto* and *de re*
possibilities.) Granted these two distinctions among possibilities,
haecceitism can be characterized as follows:



**Possibility Haecceitism**: There are distinct maximal
possibilities that differ only with respect to the non-qualitative
possibilities they include.



According to Possibility Haecceitism, maximal possibilities that
*differ haecceitistically* include the very same qualitative
possibilities and differ only in terms of the non-qualitative
possibilities they include. So, while most everyone holds that there
are maximal possibilities that differ qualitatively *and*
non-qualitatively from actuality, haecceitistic differences are
distinctive: they divide maximal possibilities that differ only
non-qualitatively.



Although Possibility Haecceitism requires quantification over
possibilities, it remains silent about possible worlds. But, for most
realists about possible worlds, quantification over maximal
possibilities requires or is simply equivalent to quantification over
possible worlds. Typically, such realist views of possible worlds
identify each maximal possibility with a unique possible world and
non-maximal possibilities with sets of possible worlds. And, while
views that reduce possibilities to possible worlds can employ
Possibility Haecceitism to express haecceitism, some might be tempted
to interpret haecceitism as a thesis about qualitatively indiscernible
worlds. Such a view would attempt to formulate haecceitism as the
following thesis:



**World Indiscernibility**: There are distinct possible
worlds that are qualitatively indiscernible.



As Lewis (1986: 220-247) and Skow (2008) point out, however,
World Indiscernibility is a misleading way to express haecceitism
given certain views about possible worlds.



According to *ersatzist views*, which identify possible worlds
with abstract entities like sentence-types, properties, propositions,
or sets, the truth of World Indiscernibility will turn, not on whether
there are distinctively haecceitistic possibilities, but on whether
such entities are qualitatively indiscernible from one another.
(*Qualitatively indiscernible* entities share all their
qualitative properties, while *qualitative duplicates* share
only their intrinsic qualitative properties.) So, if one holds that
sets or propositions have no qualitative features, then World
Indiscernibility is true, regardless of one's views about what
is and what is not possible. So, for many ersatzists, the status of
World Indiscernibility does not depend upon any distinctive modal
commitments, but is settled by apparently orthogonal questions
regarding the nature of the abstract entities with which possible
worlds are identified.



In light of disagreement about which entities play the role of
possible worlds, no characterization of haecceitism that makes
substantive assumptions about the nature of possible worlds will prove
acceptable to all ersatzists. (On ersatzism, see Lewis (1986:
136-142), Divers (2002: 167-292), and Sider (2002).)
Despite this, competing ersatzist views can employ their own
distinctive resources to provide formulations of haecceitism. For
instance, if possible worlds are identified with maximal consistent
sets of propositions, haecceitism can be taken as the claim that there
are distinct maximal consistent sets of propositions that include the
same qualitative propositions but different non-qualitative
propositions. For other versions of ersatzism, alternative strategies
for formulating haecceitism that appeal to properties, sets, or other
entities are available, but none have a plausible claim to being a
metaphysically neutral expression of haecceitism.



Although formulations of haecceitism tailored to various ersatzist
views differ significantly, they typically share a commitment to a
one-one correspondence between possible worlds and maximal
possibilities. This correspondence allows ersatzists to treat talk of
maximal possibilities and possible worlds as largely interchangeable
for most theoretical purposes. Ersatzists who accept Possibility
Haecceitism therefore commonly endorse the following thesis:



**World Haecceitism**: There are distinct maximal
possibilities that differ only haecceitistically and there is a
one-to-one correspondence between possible worlds and the maximal
possibilities they represent.



Erzatzists can, however, reject World Haecceitism, and, as we'll
see below, the resulting view is an analogue of the Lewisian modal
realist's "cheap haecceitism." But, as should be
clear from the preceding, whether a given formulation of haecceitism
is an apt one crucially depends upon the background metaphysics of
possibilities and possible worlds.



On issues that arise in formulating haecceitism, see Lewis (1986:
220-247), Russell (2013a), Skow (2008, 2011), and Stalnaker
(2011). Kaplan (1975) is an importantly early contribution where,
among other things, Kaplan attributes the use of the label
'haecceitism' to R.M. Adams. On the ways in which
Kaplan's use of 'haecceitism' departs from
now-standard uses, see Stalnaker (2011: 54-62). For other issues
in characterizing haecceitism, see Graff Fara (2009), Torza
(2012) and Scarpati (2021).


### 1.2. Haecceitism and Modal Realism



While ersatzist views identify possible worlds with abstract entities,
Lewisian modal realism identifies possible worlds with maximal sums of
(analogically) spatiotemporally interrelated entities. According to
Lewisian modal realism, for any way things could have been, there is
some possible world that represents that possibility. Moreover, these
possible worlds are no less "real" or concrete than our
actual world. (Lewis characterizes these possible worlds as
"concrete" only with reservation, given competing,
non-equivalent conceptions of the abstract-concrete distinction.)



Within Lewisian modal realism, *de re* modality is analyzed in
terms of Lewis' distinctive and controversial *counterpart
theory*. According to counterpart theory, ordinary individuals are
not numerically identical or "bilocated" across possible
worlds. Instead, possible individuals are worldbound, existing in only
one world, and possess their *de re* modal properties in virtue
of bearing counterpart relations to other possible entities. Roughly
put, counterpart theory holds that an individual \(a\) is possibly
\(F\) if and only if \(a\) has a counterpart that is \(F\), where
counterpart relations are relations of qualitative resemblance between
possible individuals. So, according to Lewis'
counterpart-theoretic treatment of *de re* modality, it is true
that Obama could have been a doctor if and only if there is some
possible individual that appropriately resembles Obama and is a
doctor. *De re* modality is therefore a matter of resemblance
relations between parts of possible worlds although the relevant
resemblance relations vary from context to context. (Lewis'
views on counterpart theory and counterpart relations change over
time, see Lewis (1968, 1986). On counterpart theory, see Graff Fara
(2009), Fara and Williamson (2005), and Hazen (1979).)



Since Lewis analyzes *de re* representation--i.e., the way
in which entities represent *de re* possibilities--in
terms of qualitative resemblance, counterpart relations never divide
qualitatively indiscernible entities. Therefore, for any
qualitatively indiscernible entities \(x\) and \(y\) in a given
context, \(x\) is a counterpart of \(z\) if and only if \(y\) is a
counterpart of *z*. This commitment has serious consequences
for the modal realist treatment of haecceitism. In particular, it
guarantees that qualitatively indiscernible possible worlds do not
differ in terms of what *de re* possibilities they represent.
Lewis therefore endorses the following thesis about the connection
between qualitative properties and what *de re* possibilities a
world represents:



**Qualitative Supervenience**: Facts about what worlds
represent *de re* supervene upon facts about the qualitative
properties of worlds.



As Lewis uses "haecceitism", it is the denial of
Qualitative Supervenience and therefore the claim that non-qualitative
features of worlds at least partially determine what worlds represent
*de re*. (On the relation of supervenience, see the entry by
McLaughlin and Bennett.) For modal realists who would reject
Qualitative Supervenience, qualitatively indiscernible possible worlds
can differ with respect to which *de re* possibilities they
represent. N*on-Lewisian* modal realists of this sort can
therefore hold qualitatively indiscernible possible worlds to
represent maximal possibilities that differ haecceitistically. But,
since Lewis endorses Qualitative Supervenience, he claims that
qualitatively indiscernible worlds represent the very same
possibilities. Positing qualitative indiscernible worlds therefore
provides Lewis with no additional resource for making sense of
haecceitistic differences. (Lewis is officially agnostic about whether
there are any qualitatively indiscernible worlds. See Lewis (1986:
224).) As a consequence, Lewis holds that we go wrong in assimilating
questions of haecceitism to questions about qualitatively
indiscernible worlds. For Lewis, haecceitism is an issue regarding how
possible worlds represent *de re* possibilities. So, even if
Lewis were to posit distinct yet qualitatively indiscernible worlds,
they would differ non-qualitatively but not *haecceitistically*
in the Lewisian sense.



Since qualitatively indiscernible worlds are no help to Lewis in
accounting for haecceitistic possibilities--e.g., where two twins
swap their qualitative roles--and Lewis does take these to
be genuine possibilities, he offers an important modification to his
earlier version of counterpart theory that seeks to accommodate such
possibilities. Lewis' modified counterpart theory permits
individuals to have multiple counterparts within the actual world.
(See Lewis (1967, 1983, and 1986).) So, in the case of our two twins,
the firstborn twin has its second-born twin as one of its
counterparts. In certain linguistic contexts, the second-born twin
therefore represents a possibility for the firstborn--namely, the
possibility of occupying precisely the qualitative role of the
second-born twin. In this way, the actual world and its parts will, in
suitable contexts, represent, not only the actualized maximal
possibility, but also maximal possibilities that differ
haecceitistically from the actualized maximal possibility. Context
permitting, each possible world can therefore represent a plurality of
maximal possibilities each of which differ haecceitistically from one
another. And, since Lewis' modified counterpart theory holds a
single possible world and its parts to represent distinct maximal
possibilities that differ haecceitistically, it accommodates the
representation of such possibilities without multiplying possible
worlds. Lewis describes this view as "haecceitism on the
cheap." Understood in terms set out above, this "cheap
substitute for haecceitism" entails Possibility Haecceitism yet
rejects World Haecceitism.



In denying World Haecceitism, Lewis forgoes a one-to-one
correspondence between maximal possibilities and possible worlds. This
feature proves significant in several discussions about the tenability
of "cheap haecceitism." Graff Fara (2009) argues that, by
rejecting World Haecceitism, cheap haecceitism cannot satisfactorily
interpret modal logic enriched with an actuality operator. Kment
(2012) also argues that cheap haecceitism delivers an inadequate
treatment of chances and counterfactuals, while Stalnaker (2008:
69-71) suggests that semantic considerations support World
Haecceitism over cheap haecceitism. On early challenges to counterpart
theory, see Kripke (1980) and Hazen (1979). On counterpart theory,
actuality, and haecceitism, see Baltimore (2014), Cowling (2013), and
Russell (2013a, 2013b).


## 2. Haecceities and Haecceitism



This section discusses the connection between haecceitism and
haecceities as well as some of the central issues regarding
haecceities and other non-qualitative properties.



Consider once again the haecceitistic possibility according to which
you do not exist and a different individual, Double, instantiates all
of your actual qualitative properties. A natural way to describe this
possibility is as one where the distribution of *qualitative*
properties is just as it actually is, but where
*non-qualitative* properties are distributed differently. In
particular, this alleged possibility is one according to which your
*haecceity* goes uninstantiated and the haecceity of a
non-actual individual, Double, is instantiated in its place.



Since haecceities like *being Napoleon* and *being identical
to Socrates* are properties uniquely tied to specific individuals,
haecceitistic differences are naturally explained in terms of
differences in the distribution of haecceities. These properties,
sometimes called "thisnesses" or "individual
essences", are typically thought to have the existence of the
relevant individuals as a necessary and sufficient condition for their
instantiation. So, for example, if Napoleon exists, then, necessarily,
exactly one thing, Napoleon, instantiates *being Napoleon* and,
if Napoleon does not exist, nothing instantiates *being
Napoleon.* In addition, facts about the distribution of other
non-qualitative properties--e.g., *being five feet from
Napoleon*--are necessitated by the distribution of
haecceities and qualitative properties. (Here, talk of
'properties' should be interpreted in the broad sense
including monadic properties as well as \(n\)-adic relations.) Most
haecceitistic differences will therefore involve differences in the
distribution of haecceities as well as additional non-qualitative
properties like *being five feet from Napoleon*.



While haecceitistic differences are commonly explained in terms of the
distribution of haecceities, haecceitism is not merely the view that
haecceities exist. To see why, notice that nominalists who deny the
existence of properties might nevertheless accept the modal
commitments of haecceitism, claiming that things could have been
different non-qualitatively without being different qualitatively. In
addition, those who affirm the existence of haecceities and other
non-qualitative properties might still go on to reject the distinctive
modal commitments of haecceitism (e.g., denying that things could
differ non-qualitatively without differing qualitatively). So,
although it is common for haecceitists to posit haecceities and employ
them in characterizing haecceitistic differences, haecceitism is, in
principle, independent of realism about haecceities given
haecceitism's ineliminable modal component.



Although haecceitism is not merely realism about haecceities, the
metaphysics of haecceities and non-qualitative properties is still
relevant for understanding haecceitism. Perhaps most importantly, some
account of the qualitative/non-qualitative distinction is needed to
interpret the thesis of haecceitism. Typically, this distinction is
introduced by way of example with haecceities like *being
Napoleon* taken as paradigmatic non-qualitative properties and
properties like *mass* and *charge* taken as
paradigmatic qualitative properties. When moving beyond these
examples, other non-qualitative properties are usually held to share
haecceities' dependence upon specific individuals. For example,
*being five feet from Napoleon* is plausibly thought to require
the existence of Napoleon while a qualitative property like *being
five grams mass* requires the existence of no specific individual.
Terminologically, non-qualitative properties exhibiting this kind of
dependence are sometimes labeled "impure properties",
"identity properties", or "haecceitistic
properties", where "haecceity" is usually reserved
properties like *being Napoleon.*



Attempts at a philosophical analysis of the
qualitative/non-qualitative distinction often take the connection
between non-qualitative properties and specific individuals as a
starting point. For example, Hawthorne (2006: 8) says:
"haecceitistic properties--such as *being identical to
John* or *being the daughter of Jim*--are those which,
in some intuitive way, make direct reference to a particular
individual(s)." But, while rough characterizations of this sort
leave the (non-)qualitative status of other kinds of properties
indeterminate or unclear, reductive analyses have been proposed with
the aim of providing a comprehensive account of the distinction. Adams
(1979: 7-9) considers an account of the distinction that ties
non-qualitative properties to certain kinds of linguistic items. Lewis
(1986, 2002) endorses views on which qualitative properties supervene
upon or are appropriately definable in terms of a distinctive class of
"perfectly natural properties." Still other
views--e.g., Rosenkrantz (1979)--aim to analyze the
dependence of non-qualitative properties on individuals and
distinguish non-qualitative properties in terms of this dependence. In
contrast, Diekemper (2009) and Cowling (2015) endorse primitivism
about the distinction between qualitative and non-qualitative
properties, taking it instead as irreducible or metaphysically
fundamental. But, regardless of one's preferred view of the
distinction, some account is owed of the qualitative status of
non-paradigmatic cases including modal properties like *being
possibly a statue*, broadly logical properties like *being
self-identical*, and, for those impressed by the analogies between
individuals and species, certain kind properties like *being a
tiger*. (See Cowling (2015), Hoffmann-Kolss (2018), Simmons
(2020), and Plate (2022) on the distinction.)



Debates about the metaphysical status of haecceities are also bound up
with more general debates about the nature of properties--e.g.,
whether properties are universals or tropes, *in re* or
*ante rem* entities, sparse or abundant, and so on. But,
regardless of one's preferred view about the metaphysics of
properties, haecceities do seem to have some distinctive features.
Unlike most other properties, haecceities are not typically thought to
be multiply instantiable--i.e., there is exactly one possible
object that can instantiate *being Napoleon*--and, as
commonly conceived, haecceities do not (without auxiliary assumptions)
ground qualitative resemblance. So, if one holds that all properties
must be multiply instantiable or ground qualitative resemblance, then
one must either reject haecceities or opt for a disunified metaphysics
of properties. (On some competing views of the metaphysical role of
haecceities, see Diekemper (2015).)



Within leading views of properties, various options are available for
developing a metaphysics of haecceities. For example, in an effort to
assimilate haecceities into a class nominalist ontology where
properties are identified with sets, Lewis (1986: 225) characterizes
haecceities as follows: "So we get properties that are in no way
qualitatively delineated, and some of these are haecceities of this-
and other-worldly individuals. A unit set of an individual is one
especially stringent haecceity. Also, for any individual and any
counterpart relation, there is the set of that individual together
with all its counterparts, and this is a less strict sort of
haecceity." The resulting view takes our talk of haecceities to
slide between talk of properties distinctive to each worldbound
individual and talk of properties shared by individuals unified by a
common counterpart relation. (On the broader conception, haecceities
are non-qualitative in nature, while, on the narrower conception,
haecceities end up being qualitative, provided there are no
qualitatively indiscernible worlds.) In contrast to this Lewisian
view, other views attribute a more significant metaphysical role to
haecceities, taking haecceities to individuate or determine the
identity of entities and therefore figure into a metaphysical
explanation of facts about identity and individuation. (Bowers and
Wallace (2018) present an argument against certain conceptions of
haecceities and their theoretical role. See Skiles (2019) for a
response.)



Views that take haecceities to provide metaphysical explanations of
the identity of individuals suggest a noteworthy connection between
haecceitism and fundamentality. In particular, if we assume that the
stock of the world's fundamental properties (provided there are
such properties) suffices to fix the distribution of absolutely all
properties, then haecceitism guarantees that qualitative properties
cannot, on their own, fix the distribution of non-qualitative
properties like haecceities. As a consequence, haecceitism points
toward the conclusion that some non-qualitative properties are
fundamental. So, for those who hold that fundamental properties are
exclusively qualitative, either the assumed conception of
fundamentality or haecceitism must be rejected. For the committed
haecceitist, a remaining option admits fundamental qualitative as well
as fundamental non-qualitative properties. On the fundamentality of
non-qualitative properties, see Bacon (2019) and Simmons (2021).



A further notable debate about the metaphysics of haecceities concerns
their modal status. Some, like Plantinga (1974), take haecceities to
exist necessarily. So, while *being Napoleon* goes
uninstantiated in possible worlds without Napoleon, it nevertheless
exists in such worlds. According to other views like that of Adams
(1981), haecceities are contingent existents, existing only in those
worlds where their bearers exist. So, although *being Napoleon*
actually exists, it neither exists nor is instantiated at worlds
without Napoleon. For discussion of this debate and cognate ones, see
McMichael (1983) and Diekemper (2015).



On the general metaphysics of haecceities, see Adams (1979, 1981),
Cover and O'Leary-Hawthorne (1997), Lewis (1986), Swinburne
(1995), and Rosenkrantz (1993). On epistemological and metaphysical
issues about haecceities--e.g., whether individuals can be
acquainted with the haecceities of other individuals--see
Rosenkrantz (1993). On haecceities and the identity of indiscernibles,
see Robinson (2000). On haecceities of mathematical entities and their
role in mathematical structuralism, see Shapiro (2006: 139) and Menzel
(2018). See McDaniel (2017: 193-194) for discussion of
how haecceities might be identified with individual ways of
being.


## 3. Haecceitism and Essentialism



Haecceitism and essentialism are controversial theses about *de
re* modality. This section briefly introduces essentialism and
then examines its interaction with haecceitism.



The *essential* properties of an individual are properties it
cannot exist without instantiating. In contrast, its
*accidental* properties are those properties that are not
essential to it. (According to the modal view of essence, this modal
characterization of essential properties provides necessary and
sufficient conditions for essentiality. On non-modal views, this
characterization merely captures a necessary condition. See Fine
(1994) for the case against the modal view.)



Essentialist theses claim that certain kinds of properties are
essential to certain kinds of individuals. For example, according to
*origin essentialism*, biological individuals have their
biological origins essentially. Origin essentialism therefore requires
that an individual like George W. Bush have his actual biological
origins--in this case, Barbara and George H.W. Bush--in any
possible world in which it exists. (On origin essentialism, see Kripke
(1979) and Robertson (1998). On other essentialisms, see Cartwright
(1968) and Mackie (2006). For a comprehensive discussion of varieties
of essentialism, see Dorr, Hawthorne, and Yli-Vakkuri (2021).)



Essentialist theses come in "stronger" and
"weaker" forms. Weaker, less interesting forms of
essentialism require that all individuals instantiate indiscriminate
properties like *being self-identical* or *being such that
\(2+2=4\)*. (Again, non-modalists like Fine (1994) deny these
necessary properties are properly counted as essential to all entities
even while *being such that \(2+2=4\)* might be essential to
the number two.) Stronger, more interesting versions of essentialism
like origin essentialism ascribe distinctive essential properties to
individuals. The strongest form of essentialism is
*hyperessentialism*, according to which each individual has all
of its properties essentially. So, for any individual, there is only
way that that individual can be.



Intuitively, essentialism limits the *de re* possibilities for
individuals, while haecceitism extends the *de re*
possibilities for individuals by admitting contentious
possibilities--e.g., the possibility where you swap qualitative
roles with Obama. It is important to note, however, that even the
strongest versions of essentialism, hyperessentialism, do not rule out
haecceitism. For, while hyperessentialism does rule out haecceitistic
differences where *you* have different properties, it does not
rule out a "mass replacement"--i.e., an alternative
maximal possibility where wholly different individuals occupy each of
the qualitative roles occupied in the actual world. These maximal
possibilities differ haecceitistically even while there is no
violation of essence, since no individual exists according to more
than a single world. (Those who reject possibilities involving
non-actual or "alien" individuals would, however, have the
makings of an argument from hyperessentialism to anti-haecceitism.)
Although essentialism provides no direct argument against haecceitism,
hyperessentialism and other strong versions of essentialism do
preclude certain kinds of haecceitistic differences where individuals
"swap" qualitative roles. For example, just as
hyperessentialism rules out any haecceitistic possibilities where you
have a different qualitative role, origin essentialism rules out
haecceitistic differences that involve organisms having anything other
than their actual biological origins. For this reason, a commitment to
strong versions of essentialism will constrain the range of admissible
haecceitistic differences.



Weak forms of essentialism have few consequences for haecceitism.
Moreover, the thesis that individuals have their haecceities
essentially is often taken as a prerequisite for a commitment to
haecceitism, since the thesis sometimes called "extreme
haecceitism" holds that haecceities are the *only*
essential properties of individuals aside from perfectly general
properties instantiated by all entities (e.g., *being
self-identical*). According to extreme haecceitists, not only
could Napoleon have been a poached egg, the world could have been
qualitatively just as it actually is but such that a poached egg and
Napoleon swap their respective qualitative roles. Extreme haecceitism
is therefore among the most permissive views about *de re*
modality and admits possibilities where you occupy the qualitative
roles of a poached egg. For this reason, extreme haecceitism is often
(albeit confusingly) classified as a version of
"anti-essentialism", by virtue of denying that individuals
have distinctive essences apart from their respective haecceities. (On
anti-essentialism and extreme haecceitism, see Heller (2005),
Stalnaker (1979), and Lewis (1986). See Mackie (2006) for a defense of
"minimal essentialism", according to which individuals
have their haecceities and belong to their ontological categories like
*property* or *object* essentially.) At the same time,
extreme haecceitism is typically paired with a commitment to the
necessity of identity and distinctness and therefore rules out
possibilities according to which actually distinct objects are one and
the same. A yet more permissive view about *de re* modality
might abandon this commitment, taking even the identity and
distinctness of individuals as accidental. (On whether
anti-essentialism is best paired with the necessity of identity and
distinctness, see Nelson (2006). On indvidual essences, see Losonsky
(1987).)



Finally, while essentialism holds certain properties as
*necessary* for being a specific individual, related
"sufficiency" theses might hold certain properties to be
*sufficient* for being a particular individual. If, for
example, we take Obama's actual qualitative role to be a
sufficient condition for an object to be identical to Obama, we
thereby rule out possibilities according to which some other
individual occupies Obama's qualitative role. (Sufficiency
theses of this sort can be hammered into essentialist theses by
holding individuals like Obama to have essential properties like
*occupying the qualitative role of the President in 2014 if the
world is qualitatively as it actually is.*) Theses of this kind
play a notable role in certain essentialist arguments--e.g., in
certain arguments for origin essentialism--but it remains unclear
how such principles might be used to offer a non-question-begging
argument against haecceitism. (For discussion of sufficiency
principles, see McKay (1986) and Robertson (1998).)



As just noted, no familiar version of essentialism provides a direct
argument against absolutely all haecceitistic differences, although
strong versions of essentialism will limit the range of admissible
haecceitistic differences. In addition, haecceitists typically assume
at least a modest form of essentialism according to which
individuals have their haecceities essentially.


## 4. Arguments for Haecceitism



This section surveys arguments for haecceitism. The most familiar of
these are conceivability arguments, which appeal to the apparent
conceivability or imaginability of maximal possibilities that differ
haecceitistically. Another line of defense takes the form of an
argument usually called "Chisholm's Paradox", which
exploits incremental modal variations in order to defend haecceitistic
differences. In addition, one might endorse haecceitism, not on the
strength of any distinctive argument, but by a more general appeal to
modal intuition, according to which haecceitistic differences simply
*seem* possible. This survey of arguments leaves aside the
general issues in modal epistemology raised by appeals to modal
intuition, focusing instead on conceivability arguments for
haecceitism and Chisholm's Paradox.



Note, also, that these arguments are most naturally taken as arguments
for Possibility Haecceitism rather than, say, World Haecceitism. So
understood, the Lewisian "cheap haecceitist" can, in
principle, accept the conclusions of these arguments even while
denying such arguments establish the existence of qualitatively
indiscernible possible worlds.


### 4.1. Conceivability Arguments for Haecceitism



Conceivability arguments for haecceitism have two steps. The first
step requires our success in conceiving or imagining certain states of
affairs. The second step requires an inference from the relevant
conceiving or imagining to the possibility of the states of affairs in
question. Among the wide variety of conceivability arguments for
haecceitism, some vary with respect to the kind of conceivability or
imagination required, while others vary with respect to the kinds of
states of affairs involved. (Cowling (2017) offers a taxonomy of these
arguments.) This section sets out some conceivability arguments
offered in the literature with some limited remarks about their
salient differences.



Black (1952) offers a now-famous conceivability argument against the
Identity of Indiscernibles, which appeals to the apparent
conceivability of a world containing only two indiscernible iron
spheres. In defending haecceitism, a natural strategy is to extend
Black's case by arguing that, not only can we conceive of a
world containing only two indiscernible iron spheres, we can conceive
of distinct worlds that differ only insofar as these spheres swap
their spatial locations. (Jubien (1993: 41-42) discusses an
argument of this sort.) A closely related argument holds that we can
conceive of a pair of worlds in which some pair of spheres has been
replaced by some other pair of spheres. Granted the conceivability of
the states of affairs in question, haecceitism follows. (A related
line of argument, owing to Adams (1979), is considered below.)



Other arguments appeal to similar states of affairs featuring
qualitatively indiscernible objects or regions. For example, Melia
(2003: 162) presents a conceivability argument that requires us to
conceive of a world that contains a single cylinder on a qualitatively
homogeneous plane. Intuitively, there are many possible directions in
which the cylinder could fall, but, since there is no qualitative
variation between these possibilities, they can be distinguished only
haecceitistically--i.e., with respect to the identity of which
regions of the plane are occupied by the fallen cylinder.



Unlike the preceding arguments, some conceivability arguments involve
a kind of "inside" or "first-personal"
imagination that requires imagining a state of affairs from the
perspective of a specific conscious individual. Compare, for example,
the act of imagining Napoleon defeated at Waterloo "from
above" with the act of imagining *being* Napoleon
defeated at Waterloo from the perspective of Napoleon. The distinction
between these imaginative acts is commonly taken as a distinction
between imagining from the outside and imagining from the inside. If
we help ourselves to this distinction, it is plausible to view several
conceivability arguments as relying upon imagination from the inside
rather than imagination from the outside. (On the distinction between
inside and outside imagination, see Nichols (2008), Ninan (2009),
Peacocke (1985), and Velleman (1996).)



Lewis (1986: 227) offers an argument of this sort, which we can take
to involve our imagining a world of one-way eternal recurrence where
the history of the actual world repeats itself *ad infinitum.*
Lewis then suggests that we can successfully imagine ourselves
occupying different "epochs"--specific recurrences of
history from the inside. And, since we can imagine ourselves occupying
different epochs, he concludes that some possibilities differ solely
with respect to whether one lives in, say, the seventeenth rather than
the fortieth epoch. In addition, Lewis (1983, 1986: 239) suggests
another conceivability argument that seems to require us
imagining living as one of a pair of twins. (Whether Lewis thinks any
robust imaginative undertaking is required here is unclear, but the
general features of this particular kind of conceivability argument is
our interest here.) And, since we can equally well imagine living as
the firstborn twin and as the second-born twin while holding the
qualitative character of the world fixed, it seems that we can
successfully imagine possibilities that differ only
haecceitistically.



Another kind of conceivability argument requires us to imagine our
nonexistence in a world qualitatively indiscernible from actuality.
Different views of imagination will deliver importantly different
verdicts about how, if at all, we might succeed in this imaginative
undertaking. (It is hard, for example, to see how we might
successfully imagine our own nonexistence from the inside.) But, among
others, Bricker (2007: 130) suggests that a plausible view of *de
re* modality must accommodate the possibility of oneself failing
to exist even while things are qualitatively just as they actually
are. (On Bricker's view, this requires only a sufficiently rich
account of counterpart relations rather than, say, qualitatively
indiscernible possible worlds. On imagining one's own
nonexistence, see Nichols (2007).)



A final conceivability argument usefully illustrates the intuitive
difference between arguments that rely solely upon outside imagination
and those invoking inside imagination. Adams (1979: 22) presents the
following conceivability argument:



> 
> Consider, again, a possible world \(w\_{1}\), in which there are two
> qualitatively indiscernible globes; call them Castor and Pollux. Being
> indiscernible, they have of course the same duration; in \(w\_{1}\)
> both of them have always existed and always will exist. But it seems
> perfectly possible, logically and metaphysically, that either or both
> of them cease to exist. Let \(w\_{2}\), then, be a possible world just
> like \(w\_{1}\) up to a certain time \(t\) at which in \(w\_{2}\) Castor
> ceases to exist while Pollux goes on forever; and let \(w\_{3}\) be a
> possible world just like \(w\_{2}\) except that in \(w\_{3}\) it is
> Pollux that ceases to exist at \(t\) while Castor goes on forever.
> That the difference between \(w\_{2}\) and \(w\_{3}\) is real, and could
> be important, becomes vividly clear if we consider that, from the
> point of view of a person living on Castor before \(t\) in \(w\_{1}\)
> and having (of course) an indiscernible twin on Pollux, it can be seen
> as the difference between being annihilated and somebody else being
> annihilated instead. But there is no qualitative difference between
> \(w\_{2}\) and \(w\_{3}\).
> 



Adams explicitly marks the move from outside to inside imagination,
noting that the haecceitistic difference "becomes vividly
clear" when we imagine the relevant states of affairs from the
perspective of the individuals involved. (See Melia (1999: 650) for a
similar argument.) 



In addressing these and other conceivability arguments for
haecceitism, anti-haecceitists have two primary lines of defense.
According to the first kind of response, the evidential connection
between conceivability and possibility is rejected--e.g., by
denying that conceivability of the relevant state of affairs is
grounds for taking the state of affairs in question to be
possible.



According to a second line of response, the apparent conceivability of
the relevant states of affairs is merely apparent. To this end, the
anti-haecceitist denies that individuals successfully conceive of or
imagine the states of affairs required to establish haecceitism.
Responses of this sort hold agents to be mistaken about the content of
their imaginings and, as a consequence, mistaken in believing
themselves to conceive of states of affairs that differ
haecceitistically.


### 4.2. Chisholm's Paradox



Chisholm's Paradox, presented in Chisholm (1967), begins
innocuously enough. Suppose that individuals are identical across
possible worlds such that *de re* modal claims like "Fred
could have been taller" are true only in case there is some
possible world where the very same individual, in this case, Fred, is
taller than he is in the actual world. Now, consider that two actual
individuals, Adam and Noah, could have had slightly different
qualitative properties. For example, Adam, instead of dying at age
930, could have died at age 931. Similarly, Noah, instead of dying at
age 950, could have died at age 949. If Adam and Noah can tolerate
these incremental "changes" to each of their qualitative
profiles, it seems that had they been a different way than they
actually are, they could have tolerated even further incremental
changes.



Now, if we allow incremental possible changes to the ways that Adam
and Noah could have been and accept the transitivity of identity, we
are committed to a finite series of incremental changes that ends in a
possible world where Adam has all the qualitative properties Noah
actually has and Noah has all the qualitative properties that Adam
actually has. This is because the relevant iterated modal claim
"Adam could have been such that he could have been such that he
could have been such" is, by our initial assumption, true in
virtue of one and the same individual, Adam, existing at different
possible worlds. So, if Adam and Noah could be incrementally different
and the individuals they could have been could also be incrementally
different, we must accept that Adam and Noah could "swap"
their respective qualitative properties. And, if so, there is a
maximal possibility that differs from actuality only in haecceitistic
terms--that is, it differs only in terms of which individuals
instantiate which qualitative profiles.



We can clarify Chisholm's Paradox as a particular schema of
modal inference. This schema involves a two-place predicate that
relates an individual and either their actual qualitative properties
(represented as \(p\_{1})\) or their possible qualitative properties
(represented as successors up to \(p\_{n})\), where differences between
\(p\_{X}\) and \(p\_{X+1}\) are small increments of qualitative
properties. In this way, Chisholm's Paradox purports to
establish that a particular individual might have had different
qualitative properties and, through iteration and the transitivity of
identity, that it might have had precisely the qualitative properties
some other individual actually has. Following Salmon (1986) and Forbes
(1984), we can present Chisholm's Paradox as follows:


* (P1) \(M(a, p\_{1})\)
* (P2) \(\Box(M(a, p\_{1})
\rightarrow \Diamond M(a, p\_{2}))\)
* (P3) \(\Box(M(a, p\_{2})
\rightarrow \Diamond M(a, p\_{3}))\)
* ...
* (P\(n\)) \(\Box(M(a,
p\_{n-1}) \rightarrow \Diamond M(a, p\_{n}))\)
* (C1) \(\Diamond M(a,
p\_{n})\)



In the version presented in Chisholm (1967), \(M\) is the relation
*instantiates each member of*; \(a\) is the individual Adam;
\(p\_{1}\) is the set of Adam's actual qualitative properties;
\(p\_{n}\) is the set of Noah's actual qualitative properties.
Chisholm's Paradox therefore involves


1. a claim about the actual world, P1,
2. a lengthy yet finite series of apparently innocuous claims about
how individuals could have been slightly different than they are,
and
3. the conclusion that Adam could have all the actual qualitative
properties instantiated by Noah.



If Chisholm's Paradox is sound, the conclusion that Adam could
occupy Noah's qualitative role entails haecceitism. This is
because Noah's qualitative properties include, not only
Noah's intrinsic properties, but also Noah's extrinsic
properties (e.g., *being such that there are seven
continents*), which suffice to fix the qualitative character of
the world. As result, if Adam could instantiate Noah's actual
qualitative properties, then the world in which he does so must be
qualitatively just like the actual world. Such a possibility therefore
entails that some maximal possibilities differ haecceitistically.



If successful, Chisholm's Paradox seems to establish not only
haecceitism, but also an extreme form of
"anti-essentialism" like extreme haecceitism. Since we can
construct a "Chisholm-sequence" with any two individuals,
unqualified endorsement of Chisholm's Paradox guarantees that,
for any individuals, there is a possible world where those individuals
swap their qualitative profiles. For instance, there would be a
possible world where Obama occupies the qualitative profile of the
Eiffel Tower and *vice versa*. As a result, neither the Eiffel
Tower nor Obama can have any distinctive qualitative properties
essentially.



While some have taken haecceitism and this anti-essentialism (or
"minimal essentialism") to be a natural package, it is
important to note that they are separate conclusions. One might reject
certain instances of Chisholm's Paradox that involve teacups
swapping qualitative roles with tornadoes, but admit that other
instances succeed in showing that distinct teacups might have swapped
their qualitative roles. Despite this, responses to Chisholm's
Paradox are typically motivated by efforts to sustain a commitment to
essentialism rather than avoid commitment to haecceitism. To this end,
some follow Salmon (1986) in holding the assumption of an
\(\mathbf{S5}\) modal logic that validates \(\Diamond P\rightarrow
\Box \Diamond P\) as the underlying culprit. (Salmon (1989, 1993)
rejects, not only \(\mathbf{S5}\), but \(\mathbf{S4}\) and
\(\mathbf{B}\) axioms.) Such responses opt for a weaker logic that
avoids (at least) the transitivity of the accessibility relation
between possible worlds. Other responses turn on the finer points of
*de re* representation. For example, while Lewis'
counterpart theory can, in non-standard contexts, accommodate
anti-essentialism, the fact that our ordinary contextual standards
rule out extreme *de re* possibilities is explained by the
intransitivity of the counterpart relation between individuals.
Another potential response to Chisholm's Paradox would be akin
to those offered in dealing with the *sorites*--e.g.,
holding that some premises of Chisholm's Paradox are false even
while we are in no position to specify precisely which ones. Yet
another line of response takes Chisholm's Paradox to deliver the
correct verdict: there are no interesting qualitative essential
properties of individuals. For example, some like Mackie (2006) take
Chisholm's Paradox to lend support to a minimal essentialist
view, according to which any object might occupy any given qualitative
role, provided it retains its non-qualitative haecceity. See Bassford
(2020) and Dorr, Hawthorne, and Yli-Vakkuri (2021: 122-219) for
additional discussion.


## 5. Arguments against Haecceitism



This section surveys arguments for anti-haecceitism. It is worth
noting, however, that for many anti-haecceitists, the denial that any
maximal possibilities differ haecceitistically issues from a broader
commitment regarding ontology or modality. (Anti-haecceitists include
Dasgupta (2009), Forbes (1985), and Robinson (1989: 400).) Consider,
for example, generalism, according to which there are no individuals.
Instead, the world is exhaustively general, comprising facts about the
distribution of qualitative properties without any facts about
individuals. Since haecceitism presupposes that there are maximal
possibilities that differ solely regarding the identity of
individuals, generalism thereby rules out haecceitism. (On generalism,
see Dasgupta (2009), Turner (2017), and Russell (2018). For discussion
of how generalists might accommodate haecceitism, see Diehl (2022).)
Similarly, necessitarians hold that there are no non-actual maximal
possibilities. Consequently, all truths are necessarily true, so there
is only one way things could have been. And, since haecceitism
requires that there are distinct maximal possibilities,
necessitarianism rules out haecceitism.



Other broad metaphysical commitments have also been claimed to support
anti-haecceitism. Armstrong (1989: 57-61) claims that
anti-haecceitism best squares with his antecedent naturalist and
combinatorialist commitments. And, just as modal intuition is
commonly taken as the grounds for endorsing haecceitism, modal
intuition is very often taken as grounds for endorsing
anti-haecceitism. For example, while Hofweber (2005: 27) is officially
neutral on haecceitism, he nicely summarizes the standard
anti-haecceitist appeal to modal intuition:



> 
> After all, could it really be that after God specified what kinds of
> things there are and what purely qualitative properties and relations
> these things instantiate, he still had many options left open about
> which objects should exist in such a world? Could God have created a
> world exactly like ours in all qualitative respects, but with the only
> difference that the thing which actually is Bush would be Clinton and
> the other way round? And could God thus create infinitely many worlds
> that are qualitatively identical and differ only in which objects
> exist in them? It seems not.
> 



Anti-haecceitists who appeal to modal intuitions in this way owe some
response to the arguments set out in the previous section. Moreover,
since modal intuitions of haecceitists and anti-haecceitists are at
direct odds, assessing the evidential weight and proper assessment of
these intuitions points towards deep methodological waters. But,
rather than taking up these issues, it will be useful to focus on two
direct lines of arguments for anti-haecceitism.


### 5.1. Against Bare Identities



One important argument against haecceitism turns on issues about the
grounding of identity facts--i.e., facts about the identity of
individuals. Set out in Forbes (1985: 128), this argument holds
haecceitism to require what we can call *bare identity facts*,
where such facts concern the identity of individuals but are not
grounded in the qualitative features of the world. Since these
identity facts can vary without any difference in qualitative
character, they are alleged to resist metaphysical explanation. On
this front, Forbes remarks as follows:



> 
> Consider the supposition that things could have been exactly as they
> are except that the steel tower in Paris opposite the Palais de
> Chaillot is different from the one actually there. To make sense of
> this supposition, it is not permitted to imagine that the tower is
> made of different metal from the metal which actually constitutes it,
> or that it has a different design, or designer, or history. The only
> respect in which the imagined situation is to differ from the actual
> world is in the identity of the tower. The extent to which such a
> difference seems unintelligible is some measure of the plausibility of
> the view that transworld differences must be grounded.
> 



On one construal of Forbes' argument, haecceitistic differences
are unintelligible and therefore objectionable because all identity
facts must be grounded in facts about the qualitative character of the
world. Accordingly, Forbes' argument requires a commitment to
the sufficiency of qualitative facts to account for all facts about
the identity of individuals. Such a commitment rules out haecceitistic
differences, but raises questions about the tenability of the relevant
constraint on identity facts. What, if anything, can be taken to
ground the facts about the identity of qualitative properties? And, if
there are at least some ungrounded identity facts, what precisely
makes bare identity facts objectionable? (On Forbes' argument,
see Bricker (1988), Yablo (1988), and Mackie (2007).)
Although the denial of bare identities is not strictly equivalent
to the denial of haecceitism, it is a small step from the former to
the latter. Accordingly, some commentators have raised concerns that
an argument for anti-haecceitism premised upon objections to bare
identities is at risk of begging the question. On the general
question of whether identity facts admit of explanation, see Shumener
(2020).


### 5.2. Arguments from the Identity of Indiscernibles



The Principle of the Identity of Indiscernibles (hereafter, PII) holds
that, if any objects share all the same properties, these objects are
identical. To avoid triviality, PII is typically interpreted with the
domain of properties restricted to what are usually taken to be
qualitative properties. (On PII, see Rodriguez-Pererya (2010, 2022),
Hawley (2009) and Della Rocca (2005).)



Since haecceitistic differences concern qualitatively indiscernible
possibilities, it is tempting to think that, since PII rules out the
existence of qualitatively indiscernible objects, it thereby
undermines haecceitism. Assessing this line of argument raises issues
about the proper formulation of PII as well as radically different
views about the nature of possible worlds. To see how these issues
hang together, it is useful to first consider how PII might be used to
argue against haecceitism within the context of Lewisian Modal
Realism. In doing so, two versions of PII need to be
distinguished.



According to the first version regarding objects within a given world,
*PII-Objects*, there are no qualitatively indiscernible objects
within a single possible world. PII-Objects therefore rules out states
of affairs like those suggested in Black (1952) involving
qualitatively indiscernible iron spheres. Although PII-Objects ensures
that no object has a qualitatively indiscernible worldmate, it is
neutral on whether or not there are qualitatively indiscernible
worlds, leaving open whether there are distinct yet qualitatively
indiscernible worlds.



A second version of PII, *PII-Worlds*, concerns possible worlds
themselves rather than the individuals within them. It holds that
there are no distinct yet qualitatively indiscernible worlds, but it
is neutral on whether there are qualitatively indiscernible
individuals within a single world. PII-Worlds therefore leaves open
whether there are worlds like Blacks' two-sphere scenario in
which there are distinct qualitatively indiscernible objects.



Having now distinguished these principles, we can consider whether
either provides an argument against haecceitism. As Lewis (1986: 224)
notes, PII-Objects leaves haecceitism untouched, since it is
compatible with the possibility of qualitatively indiscernible worlds
that differ haecceitistically. And, while PII-Worlds rules out
qualitatively indiscernible worlds rather than objects within worlds,
Lewis' cheap haecceitism still permits the representation of
maximal possibilities that differ haecceitistically even without
positing qualitatively indiscernible worlds. It looks, then, like PII
is not a plausible starting point for a case against Possibility
Haecceitism within Lewisian Modal Realism.



Does an argument against haecceitism on the basis of PII fare any
better within an ersatz view of possible worlds? It's tough to
say. As noted in Section One, different versions of ersatzism deliver
different verdicts about whether possible worlds are qualitatively
indiscernible from one another. For example, if one holds that all
propositions are qualitatively indiscernible, an unrestricted
application of PII will cause broad problems for such a
view--e.g., by ruling out the existence of more than a single
possible world. On other ersatzist views, according to which possible
worlds have distinctive qualitative characters even while they
represent maximal possibilities that differ haecceitistically, PII
will not rule out a commitment to haecceitism. In light of these
consequences, PII would need to be applied, not to the possible worlds
of the ersatzist, but, rather, to the possibilities they represent.
And, of course, if the ersatzist denies that there are maximal
possibilities that differ without differing qualitatively, they reject
haecceitism. But, since the relevant principle used to undercut
haecceitism is not, strictly speaking, PII regarding objects or worlds
but instead possibilities, it is unclear whether it merely collapses
into the straightforward denial of haecceitism. A worry, then, is that
the version of PII that suffices to undercut haecceitism is so close
to the thesis of anti-haecceitism that any argument that proceeds from
such a principle merely begs the question. In addition, it is unclear
if such a principle can be plausibly motivated without leading to
objectionable modal commitments by requiring one to reject the kinds
of possibilities that Black (1952) notes. (On the case for Black-style
possibilities involving qualitatively indiscernible objects, see Adams
(1979: 17-19).)


## 6. Restricting Haecceitism



The preceding arguments aim to show that there are no haecceitistic
differences of any kind between maximal possibilities. Other arguments
are narrower in scope and aim to establish a weaker thesis: that
certain kinds of haecceitistic differences are spurious. If
successful, these arguments will rule out only some kinds of
haecceitistic differences while falling short of providing a perfectly
general case against haecceitism. To get a sense of restricted or
domain-specific (anti-)haecceitisms, it will be useful to focus on one
example where restricted, domain-specific theses of haecceitism or
anti-haecceitism play a notable role in a core metaphysical
debate.



Consider the kind of possibility exploited in a rough approximation of
Leibniz's shift argument against absolute space: If absolute
space exists, then there is a non-actual possibility, according to
which all actual objects are uniformly shifted five feet from their
actual spatial positions. Such a possibility--let us
suppose--differs only haecceitistically from actuality. (For more
on haecceitism and spacetime, see Section 7 and the references
therein. On Leibnizian shift arguments, see Russell (2014).)



In considering this alleged possibility, a range of responses are
available: For those who believe realism about space requires
accepting such possibilities, but find such possibilities incredible,
the denial of absolute space is an available response. For other
realists about absolute space unbothered by haecceitistic differences,
the possibility in question poses no challenge. Still others might
retain realism about absolute space yet deny this apparent possibility
is a genuine one. The most natural strategy here is to claim that
certain kinds of haecceitistic differences--specifically, those
that involve merely a shift in spatial position--do not
correspond to genuinely distinct possibilities. Importantly, this
third strategy does not rule out haecceitistic differences *per
se*, but requires at least a domain-specific anti-haecceitism,
according to which there are no haecceitistic differences regarding
regions of absolute space.



In response to arguments that broach the question of haecceitism in a
limited domain, useful debate requires us to distinguish the scope of
different versions of haecceitism and the distinctive motivations of
domain-specific (anti-)haecceitisms. Naturally, one might accept
certain kinds of haecceitistic differences while rejecting others. For
example, while one might accept possibilities according to which two
twins swap qualitative roles, one might deny that you and Obama could
swap their respective roles. In addition, even those who accept these
haecceitistic differences regarding humans can deny that you could
have swapped qualitative roles with your singleton set or the Milky
Way galaxy. The question that arises for those unswayed by blanket
arguments against haecceitism is to determine which putative
haecceitistic differences between possibilities are to be admitted.
Characterizing this or that view as committed to haecceitism
*simpliciter* can therefore prove unhelpful without a
specification of the precise haecceitistic differences admitted.


## 7. Connections to Haecceitism



Haecceitism has consequences for a range of issues in metaphysics and
the philosophy of language. This section provides a brief overview of
some of the ways in which haecceitism proves most significant.


### 7.1 Haecceitism & Quidditism



Quidditism is the property-theoretic analogue of haecceitism.
(Armstrong (1989: 59) seems to coin the term
'quidditism.') But, while distinctively haecceitistic
possibilities involve individuals being "swapped" or
"replaced" without any qualitative difference,
distinctively quidditistic possibilities involve properties swapping
or replacing one another in the world's causal-nomic structure.
If, for example, there is a maximal possibility, otherwise
indiscernible from actuality, where *mass* and *charge*
swap their respective causal-nomic roles (e.g., where objects resist
acceleration in virtue of their charge), this maximal possibility
would differ quidditistically from actuality. Similarly, if there is a
maximal possibility according to which all actual causal-nomic facts
are the same except that some actually uninstantiated property,
*schmass*, occupies the causal and nomic role of *mass*,
this maximal possibility would also differ quidditistically from
actuality. (Typically, quidditism is taken as a thesis about
fundamental or "sparse" properties like *mass* and
*charge* rather than as a thesis about all properties
whatsoever.)



Like haecceitism, quidditism's proper formulation is contentious
and depends heavily upon background metaphysical assumptions. Some
formulations of quidditism invoke either maximal possibilities or
possible worlds, while modalist formulations of quidditism do without
either resource. Additionally, there is a quidditistic analogue of
cheap haecceitism, according to which a given possible world
represents various maximal possibilities that differ only
quidditistically. (On formulations of quidditism and property
counterpart theory, see Hawthorne (2002b) and Heller (2002,
2005).)



Arguments for quidditism have notable parallels with arguments for
haecceitism. Some quidditists suggest that our pedestrian modal
judgments support quidditism (see, e.g., Lewis (2009: 209), while
other defenses of quidditism can appeal to the apparent conceivability
of scenarios where properties swap their causal-nomic roles.
Additionally, Bird (2007: 74-76) considers but rejects a
property-theoretic analogue of Chisholm's Paradox that, if
successful, establishes quidditism. A different line of argument,
which has no direct analogue in the case of haecceitism, appeals to
combinatorial principles regarding the nature of modality. These
combinatorial principles hold that various permutations of fundamental
properties across, say, causal nomic roles, correspond to distinct
maximal possibilities, which, if genuine, would differ only
quidditistically. (See Lewis (2009: 209) for the combinatorial
argument and Locke (2010), Schaffer (2005: 10), and Wang
(2016) for discussion.)



Arguments against quidditism also appeal to modal intuitions. Black
(2000: 94) says, for example, that quidditistic differences are
"distinctions which my intuitions tell me are distinctions
without differences... My intuition is that to play the
nomological role of some colour or flavour is to be that colour or
flavour, at that the idea of two qualities swapping nomological roles
is thus unintelligible." Other anti-quidditist arguments turn on
its purported epistemological consequences. On this front, some
anti-quidditists (as well as some quidditists) hold that quidditism
entails that we are irremediably ignorant of the distribution of the
world's fundamental properties. (Lewis (2009) labels the
resulting view, "Ramseyan Humility." On quidditism and
humility, see also Bird (2007: 79), Hawthorne (2002b), Locke (2009),
Schaffer (2005), Shoemaker (1980), and Whittle (2006).) Additional
complaints and concerns about quidditism are diverse in character.
Locke (2012) discusses Ockhamist worries about the ontology of
quidditism and, specifically, second-order quiddities. Whittle (2006)
worries about the epiphenomenal intrinsic nature of properties, given
quidditism's alleged modal consequences. Black (2000) offers a
cardinality argument against quidditism, which holds its modal
commitments to demand the existence of proper class-many possible
worlds. Hawthorne (2002b) considers whether quidditism might
ultimately require a kind of "hyperstructuralism",
according to which absolutely any property might swap roles with any
other property including the relation of *causal necessitation*
itself. The resulting bizarre possibilities--e.g., where
*mass* and *causal necessitation* swap roles--would
deliver a *reductio* of quidditism should they prove
unavoidable.



Although haecceitism and quidditism are independent theses, since
neither strictly entails the other, their evidential relationship is
an interesting one. Given the parallels between the arguments for and
against them, it is unclear whether haecceitists ought to be
quidditists and *vice versa* or if the metaphysical
disanalogies between properties and individuals can justify endorsing
one but not the other. (On the analogies and disanalogies between
haecceitism and quidditism, see Schaffer (2005: 15-16).)


### 7.2 Haecceitism & Personal Identity



Debates about personal identity relate to haecceitism in diverse and
complex ways. Perhaps most notably, some arguments for the
"Simple View" of personal identity (alternatively, the
"Further Fact view"), according to which facts about the
identity of persons over time are irreducible and non-qualitative, are
plausibly taken as arguments for haecceitism. (On anti-reductionism
and the Simple View, see Parfit (1984: 210) and Olson (2012).) These
arguments exploit so-called "fission cases", which involve
an individual that apparently splits into distinct individuals but
without principled grounds for identifying one rather than another of
the post-fission individuals with the pre-fission individual.
According to some proponents of the Simple View, it seems possible
that that the pre-fission individual be identical to one of the
post-fission individuals while, in other physically and
psychologically indiscernible worlds, the pre-fission individual is
identical to an apparently different post-fission individual. If,
however, these are each genuine possibilities, facts about the
identity of persons over time do not supervene upon any physical or
psychological facts. And, since these are the qualitative facts
typically held to be relevant to personal identity over time, such
cases suggest that facts about personal identity over time do not
supervene upon qualitative features. In this way, the Simple View
lends support to the more general claim that non-qualitative facts
about the identity of persons do not supervene upon qualitative
facts.



In addition to its connection to the Simple View, a broader
methodological connection unites haecceitism and inquiries into
personal identity: a focus on the qualitative/non-qualitative
distinction. In debates about personal identity, appeal to exclusively
qualitative properties and relations (e.g., *having such-and-such
psychological features*) rather than non-qualitative properties
and relations (e.g., *having Bob's memories*) is commonly
taken as a constraint on a genuinely reductive analysis of personal
identity over time. So, just as haecceitism requires clarifying the
nature of this metaphysical distinction, criteria for distinguishing
the reductive and non-reductive approaches to personal identity also
rely heavily on the idea that certain properties are uniquely tied to
the identity of individuals. On the connection between haecceitism,
the Simple View, and (anti-)reductionist approaches to personal
identity, see Ninan (2009).


### 7.3 Haecceitism & Physicalism



The connection between haecceitism and physicalism is controversial.
If we understand physicalism as the unqualified thesis that physical
properties like *mass* and *charge* exhaustively fix all
other properties, haecceitistic differences present a *prima
facie* challenge. For, if some worlds differ haecceitistically but
are alike with respect to the distribution of physical properties,
then, contrary to physicalism, possible worlds or maximal
possibilities can be physically indiscernible yet fail to be
indiscernible *simpliciter*. Moreover, some follow Hofweber
(2005) in taking the irreducibility of haecceities and other
non-qualitative properties to physical properties to constitute a
challenge to more sophisticated conceptions of physicalism. (See Daly
and Liggins (2012) and Almotahari and Rochford (2012) on
Hofweber's argument. See Ninan (2009: 433) on haecceitism and
its relation to physicalism.)



A different assessment denies that haecceitism and physicalism are in
tension with one another by taking the scope of physicalism to be
restricted to qualitative properties. So understood, haecceitism has
no significance for the fate of physicalism, since haecceitistic
differences are purely non-qualitative in character. For those who
characterize physicalism as the thesis that worlds that are physical
duplicates of one another are duplicates *simpliciter*, this
response is especially plausible, since talk of
"duplication" is typically restricted to qualitative
properties. (See Stoljar (2010: 136) on the options for formulating
physicalism.)



Given the complex interaction between haecceitism and physicalism, a
natural strategy for circumventing this issue simply sets aside the
question of haecceitism in investigating the status of physicalism.
For example, in characterizing physicalism, Chalmers (1996: 367) says:
"I will always be considering worlds
'qualitatively', and abstracting away from question of
'haecceity.' That is, I will count two worlds that are
qualitatively identical as identical and will not be concerned with
questions about whether individuals in those worlds might have
different 'identities.'" The merits of bracketing
the uncertain compatibility of haecceitism and physicalism are
significant, but, for views that do hold them to be incompatible, no
such strategy will ultimately prove plausible.


### 7.4 Haecceitism & Spacetime



The Hole Argument against substantivalism purports to show that, given
some auxiliary assumptions, substantivalism illicitly requires the
truth of indeterminism. (See Norton's entry on the Hole
Argument.) Defenders of the Hole Argument take this commitment to
indeterminism to be a consequence of accepting certain models of
general relativity as genuinely distinct possibilities for
substantival spacetime. The possible models in question are typically
held to differ only haecceitistically, so, for substantivalists,
anti-haecceitism provides a route for rejecting the possibilities that
are alleged to require indeterminism. For committed haecceitists who
endorse substantivalism, some alternative strategy is required. One
available option is to revise the relevant conception of determinism
by taking it as a thesis about qualitatively discernible possibilities
rather than possibilities in general. On the resulting revision,
indeterminism requires the availability of qualitatively discernible
possibilities. As a consequence, admitting possibilities that differ
only haecceitistically would have no implications for the status of
determinism. Careful attention to the status and scope of haecceitism
therefore proves crucial for assessing this argument against
substantivalism.



In addition to Norton's entry on the Hole Argument, see Pooley
(2006) for a defense of anti-haecceitism. See Dasgupta (2017) and
Russell (2013b) on anti-haecceitism about spacetime, and Brighouse
(1994, 1997) and Melia (2009) on haecceitism and determinism.


### 7.5 Haecceitism & the Philosophy of Language



Haecceitism informs several issues in the philosophy of language
primarily through its conventional connection to realism about
haecceities. Since haecceities uniquely correspond to individuals,
realists about haecceities have a distinctive metaphysical resource
for the development of semantic theories. In addition, for realists
about haecceities who believe that all properties exist necessarily,
haecceities of nonexistent individuals provide an especially natural
metaphysical surrogate when explaining the possibility of true and
meaningful claims about the individuals in question. So, for example,
if one holds that singular terms like 'Obama' contribute
the haecceity being Obama to the singular proposition expressed by
sentences that include 'Obama', one can make sense of the
truth and meaningfulness of claims regarding Obama in worlds in which
Obama does not exist. (On this strategy, see Plantinga (1978: 132).)
The general strategy of using haecceities as metaphysical surrogates
for individuals has surfaced in debates about the philosophy of time,
where, e.g., Markosian (2004: 54-56), considers appropriating
haecceities of non-present individuals to address objections to
presentism.



Some appeals to haecceities in the philosophy of language are more
limited and nuanced--e.g., Hawthorne and Manley (2012: 204)
consider the deployment of haecceities and other non-qualitative
properties in a semantics for demonstratives--while other
applications are more general in scope--e.g., analyses of *de
re* senses or individual concepts in terms of haecceities. (For
discussion, see Chisholm (1976: 29).)