## 1. The Nature of Memory



The epistemology of memory has been the epistemology of human memory.
It's the sort of memory we are most familiar with. Perhaps this
everyday familiarity is informative enough for our epistemological
theorizing. We can do well without looking closely at how human memory
works, and the psychology and philosophy here can have a crisp and
little-trafficked border. The epistemology of memory up through the
twentieth century often carried on as if this were so. But more
recently epistemologists have favored an empirically-informed
approach.


### 1.1 Human Memory



Human memory is not one but several things or systems (Michaelian
2011c). The systems play different roles, most of which we might call
"remembering", even though the remembering may vary
notably from one system to the next. Some memory systems also help us
imagine possibilities or think about the future, however. As the entry
on
 memory
 already taxonomizes human memory systems in detail, this entry will
not. It will, however, briefly overview some of them. Psychologists
and philosophers often distinguish declarative from non-declarative
memory, which may roughly differentiate memory for accessible
information from memory for everything else. Declarative memory
includes episodic and semantic memory (Tulving 1972). How best to
divide episodic and semantic memory turns out to be delicate and
controversial. But they at least superficially differ in many ways,
including in their characteristic content. To simplify: the content of
semantic memory is propositional, while the content of episodic memory
is (a representation of) an event from the rememberer's past.
Your friend might remember *that* a strange event took place
recently, because you told her so. But despite your telling, she is in
no position to remember *the event*. Here, she is the
rememberer, and the event was in your personal past, not hers.



The epistemology of memory has focused on declarative memory, perhaps
to no one's surprise. Epistemology is the philosophical study of
knowledge and of what makes believing reasonable. The epistemology of
memory examines memory's role in this. Epistemology covers most
often the kinds of knowledge and reasonable believing that pertain to
accessible information. Declarative memory seems more relevant here
than non-declarative. Moreover, since epistemology covers most often
the kinds of knowledge and reasonable believing that have
propositional content, semantic memory seems more relevant here than
episodic. The line from remembering that *p* to knowing that
*p* makes fewer corkscrews than the line from remembering some
event concerning *p* to knowing that *p*. Consequently,
semantic memory has dominated the epistemology of memory. But in the
last few decades, episodic memory has stolen the show in the broader
philosophy of memory. It's safe to bet that a renaissance in the
epistemology of episodic memory is not far off.



Recent, empirically-minded epistemology of memory has been sensitive
to a key feature that at least some of our memory systems seem to
bear: they are constructive. It is most clearly the case that episodic
memory in particular is constructive (for the case laid out for a
general audience, see Schacter 1996, 2001). Remembering events is not
the straightforward affair we might have supposed. We might have
supposed that memory functions like an archive for the records of what
we have experienced; to learn is to deposit into the archive, to
remember is to withdraw an unchanged deposit, and to forget is for the
archive to malfunction. The prevailing view now, however, is that
memory is constructive, and not just occasionally but normally
(Michaelian 2011b, 2016). Remembering is not (simply) reproducing a
record, but generating new content.



This may seem to suggest that memory's role in our knowing and
reasonably believing is more limited than we'd thought. New
content from memory is suspicious--likely inaccurate or
unsupported--particularly if memory is *supposed* to
function like an archive. But the evidence to support this suspicion
is wanting (Michaelian 2011b, 2016). Episodic memory is generative,
but not in general at the cost of truth. Puddifoot and Bortolotti
(2019) argue, for instance, that the cognitive mechanisms responsible
for certain false memory beliefs are indeed "epistemically
innocent" , as they overall increase a subject's chances
of having other true beliefs or knowledge (see also Bortolotti and
Sullivan-Bissett 2018). Episodic memory's epistemic credentials
are not clearly comprised.
 Section 2.4
 below further explores the significance of memory construction in
epistemology.


### 1.2 Theories of memory



A theory of memory is roughly a theory of how memory works or of what
remembering consists in. Almost no theories of memory are essentially
epistemological. Almost none require any discussion of epistemology.
For that reason, this entry will say little about theories of memory
(but see entry on
 memory).
 One unique theory of memory, however, merits coverage here: the
epistemic theory of memory. Why? For one, it is essentially
epistemological. And for another, it stands apart from what most of
this entry will focus on.
 Section 2
 covers theories that, in a way, use memory to illuminate
epistemology, and epistemology to illuminate memory's
*epistemic power*. The theories comment on the conditions in
which memory provides or cannot provide some epistemic good, and why.
The epistemic theory of memory, however, uses epistemology to
illuminate the memory's *nature*. Rather than explain
knowing in terms of remembering, the epistemic theory explains
remembering in terms of knowing.



The epistemic theory places an epistemic necessary condition on
remembering. More specifically, propositional remembering requires
knowing (Anscombe 1981; Ayer 1956; Audi 2002; Locke 1971; Malcolm
1963; Moon 2013; Owens 2000; Pappas 1980; Williamson 2000). Any
subject who remembers that *p* knows that *p*. This
theory can lift a lantern to the nature of remembering, as it implies
that every necessary condition for knowing is also one for
remembering. If knowing requires believing, remembering requires it
too. If knowing requires truth, so does remembering. And so on.



Stronger versions of the epistemic theory say that remembering at a
moment requires knowing not only then but also previously. They add,
moreover, that that earlier knowing explains, or bears some other
special connection to, the later knowing. Any subject who remembers
that *p* at a moment knows that *p* then because she
knew that *p* before.



The epistemic theory faces more than one danger. To begin, it is worth
noting that the different versions of the epistemic theory generally
will not be complete theories of remembering. They state just
necessary conditions on remembering, not sufficient conditions. They
might be correct, but they do not say all that remembering is. Indeed,
they often could say much more. Suppose remembering requires knowing
because of past knowing. The "because" here masks an
omission. *How* does one know at one time because of knowing at
an earlier time? The most natural answer is: by memory. But we should
hesitate to accept that answer here. The epistemic theory is supposed
to be clarifying what remembering is. Paired with the natural answer,
the epistemic theory says roughly that to remember requires memory to
connect knowing with earlier knowing. The explanation of remembering
critically involves some residual, opaque memory activity. An
explanation minimally citing memory, or one further elucidating its
activity, might be more insightful.



A more common criticism of the epistemic theory is that knowledge
requires something that remembering does not (Bernecker 2010; see also
Audi 1995; Lai 2022). One form of the criticism goes as follows.
Knowledge roughly requires good and undiminished reason to believe.
Suppose you remember that *p*--you've come to know
that *p* and therefore have reason good enough for knowing that
*p*. Later you gain reason to doubt that *p* (see
discussion of defeaters in
 Section 2.2.3).
 Your reason to believe that *p* is no longer good enough for
knowing that *p*. But can you now remember that *p*? The
epistemic theory must say, perhaps unintuitively, you cannot. Perhaps
even worse, the epistemic theory seems to imply that you remembered
that *p* up until you gained the reason to doubt. So you
recently remembered that *p*, but can remember no longer, and
not because of any forgetting. It's because of some
learning--your gaining reason to doubt. It may instead be more
plausible to suppose the epistemic theory is mistaken. Remembering
does not require good and undiminished reason to believe, in which
case it does not require knowing.



Also, if the epistemic theory is correct, there is no remembering
falsely. Knowledge requires truth. Remembering, if it requires
knowing, also requires truth. Propositional *mis*remembering,
then, isn't remembering at all. At best it's mere apparent
remembering. It's not memory's doing. In other words,
whether a subject is remembering that *p* is not settled by the
mechanisms that produce *p* as an output for the subject and by
the functions of those mechanisms. Instead, the accuracy of *p*
also matters for whether the subject counts as remembering. The
epistemic theory is only as plausible as this consequence (cf. De
Brigard 2014).



Finally, the epistemic theory's prospects may depend on the
empirical matter of whether and how memory is generative. Perhaps
research in neuroscience and cognitive psychology could make it
plausible that propositional remembering is in some cases generative.
This would doom at least the stronger versions of the epistemic
theory. Knowing that *p* in the past would be unnecessary for
remembering that *p* now, if memory can generate *p* as
the content of some propositional remembering.



Defenses of the epistemic theory tend to suggest that its alternatives
are themselves flawed (Adams 2011; James 2017) or that the alleged
counterexamples to it are insufficiently clear (Moon 2013; Sakuragi
2013).


## 2. Memory and Justification



We seem to have epistemic justification for much of what we believe.
And memory seems to play some role in our having this justification.
Suppose appearances are correct here. Just what is memory's
role? What can memory do, what can't it do, and why? There are
many theories about the nature of epistemic justification, and they
might shed light on memory's role. Or things might work the
other way around--our intuitive judgments about memory's
role could shed light on which theories of justification are correct,
and which we should abandon. This section begins to explore
memory's relationship with justification.


### 2.1 Foundationalism and Coherentism



One way to illuminate memory's justificatory role is to turn the
spotlight to the structure of justification. Some of what we
justifiedly believe helps us justifiedly believe other things. But,
according to foundationalism, not all that justifies stands in need of
justification itself. There are foundations for our justification,
places where we need look for no further support. If there is
foundational justification, memory might provide some of it. Perhaps
memory is not relevantly different from perception, which is a good
candidate for being a basic source of justification. Visual perception
provides justification for believing how spatially distant things are.
Memory simply provides justification for believing how temporally
distant things are (Taylor 1956).



Or memory might not provide foundational support. Instead all support
it gives might come from other justifiers; it does not sit at the
bottom of the structure. Most contemporary epistemology accepts
foundationalism (see entry on
 foundationalist theories of justification).
 So, several sections below help locate memory in the foundationalist
structure. But there are alternatives to foundationalism.



One alternative is coherentism, according to which, roughly, a belief
is justified if and only if it coheres with other beliefs (see entry
on
 coherentist theories of justification).
 Beliefs that fit together well are mutually supporting, or supporting
as a set. Coherentism is not as popular as it once was, but still has
some advocates (Poston 2014). But even if coherentism is false,
coherence relations may still matter for justification. Coherence
might not create justification, but it may increase any already
present (Lewis 1946). Thanks to memory you might have several beliefs
that all fit together. If these beliefs are already justified, their
fitting together could boost their justification. And even if
coherence does not help, incoherence may hurt (Audi 1995; Olsson
2017). A poor fit among recollections might eliminate justification
that memory would otherwise help provide.


### 2.2 Internalism and Externalism



Learning can be understood as gaining evidence. And we seem to keep
some evidence over time. Presumably it is memory that does this
keeping. A natural way of understanding how memory helps us have
justification centers on the evidence we have thanks to memory. This
fits well with internalism about epistemic justification. Internalism
says a subject's justification is settled by her mental life.
Mentally identical subjects will be equally justified in having the
same doxastic attitudes toward the same propositions. Memory is part
of the mental life. We needn't look beyond the evidence memory
provides to see how it helps us have justification.



Contrast internalism with externalism about epistemic justification,
which says non-mental factors can result in differences in
justification, even among mentally identical subjects (see entry on
 internalist vs. externalist conceptions of epistemic justification).
 According to externalism, something contingent that makes no
difference to a subject's mental life can make a difference to
her justification. Her memory may tend to err, for example. This
tendency has to do with facts external to the mind--facts about
how for instance the past was. Perhaps if memory is to provide
justification, it will tend to get these facts right.


#### 2.2.1 The Problem of Forgotten Evidence



A few apparent epistemological problems of memory may favor
externalism over internalism. One of these is the problem of forgotten
evidence (Goldman 1999; Harman 1986; Owens 1999; Pappas 1980; see also
Frise 2015
 [Other Internet Resources];
 Huemer 1999; Madison 2017; McCain 2015). We tend to use evidence when
forming justified beliefs. But we also tend to forget this evidence,
even while continuing to believe. Pappas (1983: 266 n.1) thinks
"one typically loses one's original justification".
When the originally justified belief is kept but the original evidence
for it is not, its justification might be replaced by other
justification, or lost and not replaced, or not lost at all. In many
cases it is intuitive that the kept belief is still justified one way
or another. The problem of forgotten evidence is that of explaining
how this could be.



Some externalist theories seem to have an explanation readily
available. One such theory is process reliabilism (see entry on
 reliabilist epistemology).
 Very roughly, it says a belief's justification depends on the
reliability of the process that forms or keeps the belief. Memory
seems relevantly reliable. Even if a subject forgets her original
evidence for a belief that was originally justified and that she
keeps, she may keep the belief due to a reliable memory process.
Reliabilism appears able to explain how the belief is still
justified--it's because of the memory process's
reliability.



But internalist theories have other resources. A subject may have
forgotten her original evidence, but memory could still provide her
with something that justifies a belief she has kept and that was
originally justified: seeming recollection. A subject who seems to
recollect that *p* has prima facie justification for believing
that *p* (Pollock 1986). (Prima facie justification is an
epistemic good that suffices for overall justification, as long as the
subject has no reason to doubt the belief or its justification). If
that's right, seeming recollection could provide justification
even in a case of forgotten evidence. This recollection is a part of
the mental life, so internalism can appeal to it in solving the
problem of forgotten evidence.



There are different accounts of why seeming recollection justifies.
The phenomenology of a recollective experience may account for it
(Feldman & Conee 2001; Madison 2014). Or the persistence of
seeming recollection, even in the face of evidence of its inaccuracy,
may account for the justification (Brogaard 2017). Or, seeming
recollection that *p* may justify believing that *p*
because it justifies believing something else that is relevant,
namely, that one justifiedly believed that *p* in that past
(Schroer 2008).



There might be no relevant difference between, on the one hand,
*seeming* to recollect or *seeming* to remember or
*seeming* to recall and, on the other, recollecting or
remembering or recalling. Seeming to recollect may be sufficient for
remembering. But it is insufficient for knowing. (One might, after
all, seem to recollect a falsehood, but one cannot know a falsehood.)
If seeming recollection suffices for remembering, then the epistemic
theory of memory appears mistaken. The epistemic theory, again, says
that a subject who remembers that *p* knows that *p*,
perhaps because of her past knowing that *p*. But some seeming
recollection would allow remembering without knowing.


#### 2.2.2 The Problem of Stored Beliefs



Even if seeming recollection solves one problem, it is a resource of
limited use. It does not obviously account for all the justification
memory provides. It is plausible that at any given time, thanks to
memory, we have a vast number of beliefs. But we are not seemingly
recollecting the content of all these beliefs. Indeed, at best we
recollect the content of few at any particular time. The beliefs we
are not recollecting are sometimes called "stored" or
"dispositional" or "nonoccurrent". Some of
these beliefs are justified. The problem of stored beliefs is that of
accounting for this justification. (Pappas 1980 discusses a
knowledge-version of the problem).



If internalism is true, something mental other than seeming
recollection accounts for this justification. But it's at least
initially difficult to see what that might be (Goldman 1999; Senor
1993; Moon 2012a presents internalism with a knowledge-version of the
problem). Externalist theories like reliabilism, however, can still
say the reliability of the memory process responsible for these stored
beliefs helps justify them.



Seeming recollection apparently does not solve the problem of stored
beliefs. But something closely related might help. It's not just
recollecting, but *being disposed to recollect*, that helps
justify (Audi 1995; Conee & Feldman 2011; Ginet 1975; McCain 2014;
see also Feldman 1988; Piazza 2009). Having a disposition to recollect
*p* provides justification for believing *p.* Typically,
a justified stored belief is one the subject is disposed to recall.
This disposition makes sense of the stored belief's
justification. Or perhaps a seeming to recollect can itself have a
dispositional status, just as a belief can have this status, and so
seemings do justify the right stored beliefs after all (Madison
2014).



It is controversial whether recollective dispositions justify. McGrath
(2007) argues they do not, for if they do, it follows there is
justification in some cases of forgetting where intuitively there is
no justification. Kelly (2016) argues that what matters for
justification is not a recollective disposition, but instead
remembering, and not all remembering involves a recollective
disposition. Frise (2017a) argues that it is insufficiently clear just
when a subject has a recollective disposition, and also that in some
cases in which a subject is disposed to recall that *p*, the
justified attitude for her toward *p* is nonetheless suspending
judgment rather than believing. McGrath (2016) and Senor (1993) press
a more basic question: exactly why is a disposition to recollect
justifying evidence?



Not all attempts to solve the problem of stored beliefs appeal to
recollective dispositions or even to the reliability of the processes
that keep stored beliefs. One potential way out is neutral between
internalism and externalism. It denies there are stored beliefs at
all, so there is no justification of stored beliefs to account for.
Frise (2018a) argues that if representationalism--a leading
theory on the nature of belief--is true, then we have no stored
beliefs. This is because human memory turns out not to function in the
ways required for storing beliefs. According to representationalism,
believing that *p* requires bearing a special relation to a
mental representation that *p* (see entry on
 belief).
 Frise argues human memory does not store many representations, and
that our relation to stored representations is generally
underdetermined. Representationalism may be false. But if true, the
problem of stored beliefs is illusory.


#### 2.2.3 The Problem of Forgotten Defeat



Seeming recollection seems to help solve the problem of forgotten
evidence, but to help little with the problem of stored beliefs. And
there may be a further concern about whether seeming recollection
helps even with the first problem. The concern has to do with a
different sort of forgetting. A subject might form a belief without
justification, and then keep the belief while forgetting how it came
about. Or, the subject might have some reason to believe that
*p* and some reason to doubt that *p*, and go on to
believe that *p* and eventually forget the reason to doubt. A
reason to doubt or not believe is sometimes called a
"defeater" . Forgetting a defeater, which here includes
forgetting that a belief arose in the absence of justification, might
matter for overall justification. It might matter even for prima facie
justification. The problem of forgotten defeat is that of accounting
satisfactorily for justification in cases of forgotten defeat.



Forgetting defeat is not pivotal if seeming recollection justifies.
Suppose a subject who seems to recollect that *p* has prima
facie justification for believing that *p*. A subject might
have formed a belief that *p* without reason, kept the belief
but forgotten how it came about, and now seems to recollect that
*p*. The seeming recollection results in prima facie and
overall justification, even though this is a case of forgotten defeat.
Intuitions about whether there can be either sort of justification in
a case of forgotten defeat, then, bear on whether seeming recollection
justifies. These intuitions, then, bear on whether the seeming
recollection solution to the problem of forgotten evidence is
viable.



Many deny that forgetting a defeater can result in an increase in
justification (Annis 1980; Goldman 1999; 2009; Greco 2005; Huemer
1999; Jackson 2011; Senor 2010, 2017; Teroni 2018). According to Senor
(2010), a belief should not "become justified simply on the
basis of being retained". But it appears this could occur when a
defeater is forgotten. According to Teroni (2018), a belief that
*p* with defeated justification has, when the defeater is
forgotten, bad etiology. Seeming to recollect that *p* in a
case of forgotten defeat explains why the subject is inclined to judge
that *p* is true, but does not explain why this judging is
justified. Jackson (2011: 569) puts it simplest: "garbage in,
garbage out". What memory delivers is no better than what it
originally received, regardless of any forgetting in the meantime.
Senor (2007) offers further reason to deny forgotten defeat can
increase justification: there should be a kind of parity in the
positive and negative effects of what we forget. Just as there is no
decrease in justification when we forget supporting evidence, there
should be no increase in justification when we forget reason to
doubt.



According to others, forgetting a defeater can result in an increase
in justification (Bernecker 2010; Feldman & Conee 2001; Dogramaci
2015; Feldman 2005; Lackey 2005, 2007; McGrath 2007). For Feldman
(2005) and McGrath (2007), one reason to suppose there is an increase
in justification is that the subject might have lost reason to doubt.
The subject may then be left only with reason to believe, or at least
with no reason to stop believing. Believing looks like the best
option. Feldman and Conee (2001) and Lackey (2007) argue that a
subject who knows herself to be a generally careful believer has
support for a memory belief of uncertain origin, even when a defeater
for the belief has been forgotten. Lackey (2007) notes that forgetting
evidence and forgetting defeaters can indeed have asymmetrical effects
on justification, so intuitions about cases of forgetting evidence can
be uninformative about cases of forgotten defeaters. Dogramaci (2015)
argues that the pragmatic function of critical language is to promote
trustworthy testimony. But criticism will not promote that in normal
cases of forgotten defeat. This is because the subject has forgotten
why she originally formed her belief. So it is mistaken to identify
the forgetter's belief as unjustified.


### 2.3 Time-slice and Historical Theories



The problems of forgotten evidence and forgotten defeat have to do
with the justification a subject has at one time, given what the
subject has forgotten since an earlier time. If these problems
aren't just superficial, the subject's past matters for
her present justification in a nontrivial way. A *trivial* way
that it could matter is as follows: a subject had some justifying
evidence at an earlier time, and her memory causes her to have this
evidence now, and this evidence justifies her beliefs now. There is a
trivial connection here between the subject's present
justification and her past, in that the subject's past only
indirectly affects her present justification. It affects her present
justification just by affecting what evidence she has in the present.
But ultimately it is just her evidence now that determines what
justification she has now.



In short, some of the problems above draw attention to how a state of
affairs at a time might directly matter for justification at another
time. If a subject can have justification for believing that
*p* now even if she has forgotten her original evidence for
*p* and has no other support for *p* now, it appears her
past can directly affect her present justification. It is because she
*had* justification or justifying evidence that she
*has* justification. Similarly, if a subject who seems to
recall that *p* can fail to have justification for believing
that *p* now because she has forgotten a defeater for
*p*, her past seems to directly affect her present
justification.



It is not obvious just how time and justification connect, and the
role memory plays in this connection. The basic options are few. Here
are some: it could be that all that directly matters for justification
at a time is how things are at that time. Call a theory that implies
this a *time-slice* theory of justification. Or, it could be
that past states of affairs also directly matter for justification at
that time. Call a theory that implies this a *historical*
theory of justification. (See Kelly 2016 and Moss 2015 for further
discussion). A less explored possibility is that future states of
affairs directly matter for justification at a time--but since
time-slice and historical theories are the two most popular
candidates, this entry focuses on them. To include memory in these
options, and to center on the present: perhaps memory affects a
subject's justification now only by way of how her memory
currently is or is active--for example what a subject now recalls
or is disposed to recall or otherwise has tucked away in memory. Or,
perhaps what was once a part of a subject's memory also matters
for her justification now even if it is not in her memory now. Or
perhaps what she will later remember matters for her justification
now.



Note that the time-slice and historical distinction crosscuts the
internalism and externalism distinction. Wherever a theory of
justification lands in one distinction, it could land anywhere in the
other. For example, an internalist theory of justification can state
that just the way a subject is now, including the way her memory is
now, directly matters for her justification now (Feldman & Conee
2001). Or it could state that elements of her past, including its
influence on a subject's memory, directly matter for her
justification now (Huemer 1999; McGrath 2007, 2016). Some combinations
are more common and perhaps more plausible than others. Internalists
more often favor time-slice views, while externalists more often favor
historical views. Goldman's (2009) reliabilism is a paradigm
externalist, historical view: a memory belief's current
justificatory status is chiefly a matter of memory preserving the
belief's past status, and that the past status is partially
determined by factors external to the subject, such as the reliability
of the process that originally formed the belief. An externalist
theory could be time-slice, but that is less common.



Time-slice theories have some assets. For one, they are relatively
simple. On a time-slice theory, what explains a subject's
justification at a time is just the way things are then. It is more
complicated to identify the way things are at other times as also
being relevant. Moreover, the way things are at a time might fully
explain a subject's justification then. For example, a
subject's recollective dispositions and what she seems to
recollect at a time might account for all her justification from
memory then. Appealing to the past seems unnecessary. And it's
plausible that a simpler explanation, all else being equal, is better.
So time-slice theories, all else being equal, appear better than
historical theories, since the latter cite the past as also directly
mattering for a subject's present justification. Another asset
of time-slice theories may be this. Two subjects can have different
pasts but be identical in the present. They at the moment have all the
same beliefs, memories, experiences, and so on. Because they are the
same now, it might seem that they are the same with respect to what
they are justified in believing, disbelieving, and suspending judgment
in now. But if that's right, their differing pasts don't
matter (Moon 2012b). If the differences in their pasts don't
matter, it appears their pasts don't matter at all. And if
subject's past doesn't matter, it's hard to see what
else about the past could matter. Justification in the present is
settled just by how things are. Similarly, it might seem that a past
that a subject currently has no memory of shouldn't matter for
her present justification (Feldman & Conee 2001).



But historical theories might have their own merits. For example, the
causal history of a belief appears relevant to its justification in
the present (Goldman 1979). It is not just the immediate cause of a
belief that counts. How a belief originated and has since been kept in
memory, and what justificatory status it has had along the way, might
seem to directly bear on its justificatory status now. An historical
theory of justification can accommodate these intuitions, while a
time-slice theory must deny that the causal history of a belief
matters as such. For the time-slice theory, this history could matter
for justification in the present only indirectly, insofar as it
affects the world in the present. The past, including past memory,
doesn't matter for justification, except insofar as it affects
the present, which does matter for justification.



Historical theories may have an easier time explaining how reasoning
is able to provide justification. Most reasoning is temporally
extended. It takes place over time. Burge (1993: 463) says that
"Any reasoning in time must rely on memory". To reason to
a supported conclusion, presumably all steps of reasoning along the
way need to be supported too. Burge (2003: 300) thinks that it is
memory that holds any support for past steps constant during later
steps of the reasoning. When arriving at a supported conclusion, the
subject might not be thinking about evidence for the earlier steps in
the reasoning or doing anything else that would support these steps.
The subject must be inheriting support for these steps from the past
via memory. The subject's current step of reasoning
couldn't itself fully support the conclusion. We must cite the
support that memory ushers in from the past for previous reasoning
steps.



Buoying historical theories further, Kelly (2016) looks at a case of
extended reasoning that involves a nontrivial error. At the end this
reasoning the subject may end up mentally identical to a subject who
reasoned without error. (The rest of the world at that time may be
identical too.) It's plausible that the subjects are unequal in
their justification, since one of them reasoned erroneously and the
other didn't. But because the subjects are identical mentally at
the later time, a time-slice theory must say the subjects are
identical in their justification then.



Annis (1980) thinks historical theories are better at accounting for
the justification that children have. A child's current mind may
not yet be sophisticated enough to explain how some of her current
justified beliefs in memory are indeed justified. Rather, what
justifies these beliefs now must be found in the past. Annis also
argues time-slice theories flounder on the problems of forgotten
evidence and forgotten defeat.



One historical theory of particular note is epistemic conservatism
(Harman 1986; McCain 2008, 2019; McGrath 2007, 2016; Poston 2014).
According to epistemic conservatism, a subject who believes a
proposition has some prima facie reason to continue believing it.
Unless a subject has reason to drop her belief, she has some
justification for keeping it. This theory is historical because it
says having a belief at one time directly results in having
justification for it later. Past believing matters for justification
in the present. Notably, this theory is also friendly toward
internalism, and it is internalists rather than externalists who tend
to be friendly toward it. It identifies elements of the past that
affect the subject's present justification, but these elements
are all mental, namely, the subject's past beliefs. McGrath
(2007) brings epistemic conservatism to bear on a range of
epistemological problems of memory. He (2007: 14) thinks it solves the
problem of forgotten evidence. A subject may have forgotten her
original evidence for her belief that *p*, and yet it might be
intuitive that this belief is still justified. Epistemic conservatism
can explain why: the subject had already believed that *p*, and
this past believing, in the absence of a defeater, is enough for her
belief to be justified now. McGrath (2007: 21) also thinks epistemic
conservatism solves the problem of stored beliefs. A justified belief
that is stored in memory is presumably one that was believed a moment
ago too. Believing then explains why the belief is justified now.



This solution to the problem of stored beliefs faces challenges (Frise
2017a). A subject, Ric, may have justified stored beliefs. An evil
demon could bring about another subject, Vic, who is mentally
identical to Ric. When Vic comes about, he too has stored beliefs. But
he had no beliefs prior to existing. Epistemic conservatism does not
explain how any of his stored beliefs could be justified at the moment
of his creation. And there is reason to think some are justified
then--Vic is Ric's mental twin, and Ric's has
justified stored beliefs then. What's more, Vic might not change
at all mentally from the moment of his creation to the next moment.
But because Vic has beliefs at this first moment, according to
epistemic conservatism, he has prima facie justification for them at
the second moment. Epistemic conservatism explains the justification
of his stored beliefs at the second time but not the first, even
though he is his own mental duplicate at these times.



Epistemic conservatism may also solve the problem of forgotten defeat
(McGrath 2016). When a subject has forgotten all defeaters, she has no
reason to abandon belief. For her to change from believing to not
believing for no reason looks unreasonable. Keeping the belief looks
reasonable. Epistemic conservatism explains this, as it says in the
absence of defeat the past believing results in justification for
continuing to believe. Beliefs in memory that aren't based on
other beliefs are "innocent until proven guilty" (McGrath
2016: 80).



Epistemic conservatism and certain other historical theories may face
a problem specifically concerning memory. Suppose a subject
justifiedly forms a belief that *p*. Later, she remembers that
*p*. The remembering might justify believing that *p*.
But historical theories like epistemic conservatism say that past
believing or past justified believing confers justification via
memory. So it looks like the remembering subject now has two sources
of justification for the belief that *p*: the remembering and
the past believing. If having these two sources increases
justification, it appears that memory is *boosting* the
justification. Remembering can ratchet up justification. But that
seems incorrect (Bernecker 2008; Huemer 1999).



There may not be a boost in justification in this sort of case,
however, but rather an overdetermination of belief (McGrath 2007).
There are two justifying causes for the belief. It doesn't
follow that the belief has more justification than if it had one
justifying cause. One nuanced version of epistemic conservatism offers
another response. On it, belief that *p* confers justification
for continuing to believe that *p* only if the subject has no
evidence for or against *p* (Poston 2014). If remembering that
*p* is evidence for *p*, then the past believing is not
justifying the subject in continuing to believe that *p*. On
this response, then, the case of remembering while retaining past
belief involves only one source of justification. So there's no
boost upon remembering.



A variation of the boost objection is that a subject might retain her
original justifying evidence for *p*, and might thanks to
memory believe that *p*. It might appear that on epistemic
conservatism, the subject again has two sources of justification. But
the subject should not have any degree of justification beyond what
the original evidence confers. One reply to this boost objection is
that believing while retaining the original evidence here may not
result in a greater degree of justification, but simply result in
justification that is more difficult to defeat (McGrath 2016: 81).



The most popular and influential historical theory of justification is
process reliabilism. As noted, it links the justification of a belief
with the reliability of the process that yields the belief. One
sufficient condition it states for justified belief puts memory and
the past in the forefront. A process that yields beliefs could have a
range of types of inputs. Some of these inputs could themselves be
beliefs. An inferential process, for example, takes beliefs as inputs
and yields a belief. Reliabilism says that if these input beliefs are
justified, and the process has a certain kind of reliability (namely,
it tends to yield true belief when the belief inputs are true), then
the resulting belief is justified (Goldman 1979). This helps explain
how memory can justify, and how the past directly matters for present
justification. Some memory processes are reliable in the relevant way.
And a memory process can take a past justified belief that *p*
as an input and yield belief that *p* as an output later.
(Continuously believing that *p* via memory may be due to a
memory process feeding the belief that *p* into itself.) The
output belief is, according to reliabilism, therefore justified.



Reliabilism might solve several epistemological problems of memory
(Goldman 2009, 2011; Senor 1993, 2010). Consider the problem of
forgotten evidence. On reliabilism, forgetting the original evidence
for a belief need not compromise its justification. If the belief was
justified and has been kept by a suitably reliable process, it is
justified now. And consider the problem of stored beliefs. On
reliabilism a belief that is stored in memory can be justified in the
same way as in cases of forgotten evidence, even if nothing in the
subject's current mental life is justifying evidence for the
belief. Finally, consider the problem of forgotten defeat. Suppose a
subject had a defeater that eliminated all her justification for a
belief. The belief that enters memory is unjustified. The belief may
be an input to a suitably reliable memory process, but because the
input belief itself is unjustified not all inputs to the process are
justified. So even if the defeater is forgotten, reliabilism is not
implying here that the output of this memory process is justified; the
sufficient condition for justification has not been met. Reliabilism
can deliver the result that there is no justification in a case of
forgotten defeat, and maybe that result is correct. Reliabilism faces
many criticisms (BonJour 1980; Cohen 1984; Conee & Feldman 1998;
Frise 2018d). But many think it fares well in the epistemology of
memory.


### 2.4 Preservationism and Generativism



Reliabilism and epistemic conservatism differ considerably. Still,
there is common ground, and not just because both are historical
theories. They agree that the past matters for present justification
in a specific way; they each imply a thesis sometimes called
"preservationism". More than one thesis in the
epistemology of memory bears this name, however (Frise 2015
 [Other Internet Resources]).
 It is important to see how they are distinct.



One thesis called "preservationism" has to do with how
memory is not or does not function like a traditional foundational
source of justification, such as perception. The thesis, roughly, is
that memory can at best preserve justification from other sources of
justification, but memory cannot generate justification. At its core
this thesis is about a limit to memory's justificatory power.
Memory does not generate justification. It might preserve
justification, but perhaps it fails at even that. Strictly speaking,
this preservationism itself has no implications about whether the past
directly matters for justification in the present. In other words, the
thesis need not be historical, though it usually is bundled together
with historical views.



A distinct thesis called "preservationism" has to do with
memory's justificatory power, not a limit to its power. It
states, roughly, that a belief entering memory with justification
keeps it. Memory sustains justification when sustaining a belief that
had justification. This thesis itself says nothing about whether
memory can or cannot generate justification. When stated carefully
this preservationism is typically an historical theory of
justification. Memory delivers justification in the present to a
belief that it keeps and that had justification in the past. Like the
other thesis called "preservationism", this thesis is also
often bundled together with other views, and sometimes the two
preservationisms are endorsed at once, which can obscure that they are
separable.



The second preservationism is the common ground between reliabilism
and epistemic conservatism, at least if memory is relevantly reliable
(Frise 2017b). Suppose a reliable memory process receives as an input
only a justified belief that *p*, and yields belief that
*p* as an output. Reliabilism implies that the output belief is
justified. Memory is delivering justification to a belief it held onto
and that had justification. And epistemic conservatism says even mere
believing provides justification for retaining belief. Justified
believing must be able to do as much.


#### 2.4.1 Preservationism as Anti-generativism



Because these preservationist theses are distinct they merit separate
discussion. The lion's share of the literature on
preservationism is on the first thesis: memory can at best preserve
justification, but cannot generate it. Preservationism of this stripe
is popular (Annis 1980; Goldman 2009, 2011; Jackson 2011; Naylor 2015;
Owens 2000; Senor 2007, 2010). While there are arguments for this
view, it sometimes is treated as though it has a default status. It
has borne the crown since it was born. Arguments for it are
unnecessary. Opposing views, rather, are what require arguments.
Perhaps preservationism has attained this status because it seems
intuitive or simply common sense to many. And it is not hard to see
why it seems like common sense, given our common sense understanding
of how memory works: memory accumulates and keeps information from
other sources. It's not adding information. It's only
natural that memory would at best accumulate and keep justification
from these sources. It's not adding justification.



The main view that denies this preservationism says, roughly, that
memory can generate justification. Aptly enough, this view is called
"generativism" (or "generationism"; Michaelian
2011b). If memory can generate justification, one plausible way it
might do so is by way of remembering or seeming to recollect. As
noted, some responses to the problems of forgotten evidence and stored
beliefs are that seeming recollection, or perhaps also a disposition
to recollect, can justify. If a subject's seeming to recollect
that *p* results in her having justification for believing
*p* that she did not previously have, memory appears to be
generating this justification. Unsurprisingly, generativism is popular
among those who think seeming recollection justifies. Because
preservationism and generativism deny each other, and generativism is
the positive thesis and preservationism the negative, preservationism
is sometimes called "anti-generativism" (Frise 2015
 [Other Internet Resources]).



In favor of preservationism over generativism, Senor (2010) says
memory's *job* is preservative, both with respect to
belief and the justificatory status of belief. Naylor (2015) and Senor
(2017) think preservationism helps explain what happens with stored
beliefs, in a way that might help solve the problem of stored beliefs.
Presumably, the justification of stored beliefs does not increase
simply by the beliefs being stored in memory. And this is what
preservationism predicts. Preservationism also seems to help with the
problem of forgotten defeat. In a case of forgotten defeat, a subject
forgets a defeater for the justification of a belief. Goldman (2009)
and Jackson (2011) find it plausible that memory will not increase the
justification of that belief. And preservationism seems to predict
just this too. Senor (2017) adds that, even if memory can generate
justification, this is rare. More often, memory inherits justification
from other sources.



Nuanced versions of and arguments for generativism abound. In favor of
generativism over preservationism, Owens (1996) and Lackey (2005,
2007) cite cases of recalled but previously unattended to information.
A subject may witness an event, and store in memory certain details
about it that she does not notice until later. Only well after the
event does she remember the details and form a belief about them. The
belief seems justified, and memory is generating this justification.
Michaelian (2011b) notes that in this sort of case, however, memory
had stored information and then generated new justified belief in it.
But the *information* was not new. Bernecker (2010) notes that
the justification from memory in this sort of case is merely doxastic,
not propositional (it is the justification of an attitude, not
justification for having the attitude). The propositional
justification for the believing the remembered details originated from
perception at the time of witnessing the event, not from memory.



Michaelian (2011b) argues that memory can do more. It can generate new
content and, on reliabilism, new justification for belief in it,
because memory is reliable. (Similarly, Huemer 1999 argues that
seeming to remember can generate new justification for belief in new
content.) Fernandez argues (2016) that memory can generate new
justification for belief in *specific* new content. He argues
that an episodic memory contains information about how the memory
itself originates from earlier perception of the way the world was.
This information about the memory's origin is new--it was
not part of content of the earlier perception of the world. Memory
generates this new content and, because memory is reliable, it can
generate justification for believing the new content.



Lackey (2005) and Bernecker (2010) identify another sort of case in
favor of generativism. A subject may have a misleading defeater for
the justification for her belief that *p*. The defeater can
then be lost (perhaps due to forgetting). Thanks to memory the subject
still has the original justification for believing that *p*. So
it looks like the subject's belief that *p*, thanks to
memory, is now justified. Senor (2007) points out that the
justification in this sort of case is overall, but not prima facie.
Memory is not generating new support, but is instead preserving
previously defeated support that then ceases to be defeated.



Bernecker and Grundmann (2019), in support of generativism, cite cases
of incomplete remembering. Here, memory pares down the content of a
belief that may not have been acquired well. Incomplete remembering
can make up for the initial poor belief formation, perhaps by
simplifying the believed information and thus making it more likely
true. The original belief may not have been reliably formed. But
incomplete remembering reliably forms a new belief, and so the belief
is justified. This justification originates from memory.



Frise (2021) argues an extreme form of generativism follows from
reliabilism. The extreme form says memory can generate justification
even for an otherwise unjustified belief. On reliabilism, memory does
this by overdetermining belief. Memory might preserve a
subject's belief that *p* that had been formed without
justification. Independently of her already believing that *p*,
the subject might now reconstructively recollect that *p*. For
that reason also she believes that *p*. This recollection is
reliable. On reliabilism, the belief is now justified. But if
that's right, then reliabilism is less historical of a theory
than it had seemed. Memory does not always preserve a belief's
past justificatory status. If the case of overdetermined belief counts
as a case of forgotten defeat, then even reliabilism allows for
justification in cases of forgotten defeat.



Generativism and preservationism may be able to broker an uneasy
truce. Perhaps certain types of memory (such as episodic memory) can
generate justification but others (such as semantic memory) only
preserve it (Teroni 2014). Perhaps memory can generate justification
for new beliefs but not for unjustified beliefs it simply stores
(Huemer 1999; Senor 2017). Or perhaps memory can generate
justification, but not knowledge (Audi 2002).


#### 2.4.2 Preservationism as an Historical Theory



The other thesis called "preservationism" says, again,
that a belief in memory keeps its justification over time. If a
subject believes that *p* with justification at one time, and
her belief that *p* stays in memory later, then her belief that
*p* is prima facie justified at the later time. There is less
discussion of this preservationist thesis than the other. But it is at
least as popular as the other. Its proponents are numerous (Annis
1980; Bernecker 2008; Burge 1997; Goldman 2009, 2011; Harman 1986;
Huemer 1999; McGrath 2007; Naylor 2012; Owens 1999; Pappas 1980; Senor
2010). A knowledge version of this preservationism thesis is also
popular (Locke 1971; Malcolm 1963; Martin 2001; Shoemaker 1967).



Preservationism is attractive in part because it may help with a kind
of skepticism (Shoemaker 1967). We find ourselves with many beliefs,
and many of them seem justified. What accounts for their
justification? Our present support for those beliefs may not fully
explain their justification. But if beliefs inherit justification from
the past, that might explain the justification of many in the present.
Similarly, preservationism seems to help with the problems of
forgotten evidence and stored beliefs (Goldman 2009, 2011). Even if a
subject forgets the original justifying evidence for her belief,
memory hangs on to the past justifiedness of the belief in the
present. If a subject has a belief stored in memory that had been
justified, memory hangs on to its justification, even if nothing in
the subject's current mental life justifies the belief.
Preservationism also fits with a natural understanding of
memory's main function, namely, that it is preservative. Memory
stores information and attitudes toward information. It's
plausible that memory also stores the justificatory status of these
attitudes.



Note that this version of preservationism is compatible with
generativism; this helps illustrate how the two versions of
preservationism are distinct. On this version of preservationism,
memory keeps justification in certain cases. But this version says
nothing about the *limits* to memory's justificatory
power. It could be that memory also generates justification in some
other cases, as generativism says it can. This version of
preservationism is incompatible, however, with time-slice theories of
justification. Preservationism here allows a subject to have
justification at one time because she had it at another time. The way
the subject or world *is* now does not fully explain why the
subject has justification now. Rather, the way the subject or world
*was* directly affects her justification now. But on a
time-slice theory of justification, nothing outside a time directly
matters for justification at that time.



While this preservationism is a standard view, problems for it have
bubbled to the surface. Three problems concern preservationism's
consequences for the *degree* of justification that memory
allegedly preserves. Justification may not simply be binary (fully
present or absent), but instead come in a range of greater and lesser
strengths. If preservationism has implications about the degree to
which memory preserves justification, the most natural view is that
the degree of justification stays the same. But according to Huemer
(1999: 354) "The passage of time introduces new possibilities of
error; therefore, it lowers one's justification for believing a
proposition". The idea is that as time goes on memory could be
erring, and so this possibility diminishes justification over time.
Yet preservationism seems to say the degree of justification stays
fixed.



It is not entirely clear which possible errors this problem centers
on, nor whether the mere passage of time matters. Suppose just a
moment has passed--must justification decrease? Perhaps only
longer intervals of time matter. But suppose two subjects start out
the same mentally, and end up the same again mentally, but only after
notably unequal amounts of time (e.g., it takes one subject a year to
end up mentally as the other subject is after just an hour). Perhaps
not even a longer interval itself results in less justification.



Here is a second problem for preservationism that has to do with
degrees of justification (Frise 2017b). Suppose a subject formed a
justified belief that *p* in the past and still believes that
*p*, and has no relevant defeaters. The subject now wonders
whether *p* is true, but does not recall. Does this failure to
recall lower the subject's justification for believing
*p*? If so, it is hard to explain this lowering of
justification in a way that is friendly to preservationism; rival
theories offer simpler explanations. If not, preservationism has
strange results. In a case of retrieval failure it allows a
subject's belief that *p* to be as justified as it would
be if she had successfully recalled that *p*. But had the
subject only *dimly* recalled that *p*, presumably her
justification would be lower than if she had successfully recalled
that *p*. It then follows that dimly recalling is worse than
trying and not recalling at all. Dim recollection results in less
justification than failed recollection does, on preservationism.



A final problem concerning preservationism and degrees of
justification has to do with forgetting (BonJour 2016; Kelly 2016). A
subject might forget evidence that had justified her belief that
*p* to a very high degree. It's plausible that forgetting
this evidence should at least somewhat affect the degree of
justification she has for *p*. But preservationism runs afoul
of this if it implies that the high degree of justification remains.
The level of justification might decay over time in cases of forgotten
evidence. Still, perhaps it never fully decays. If it does not, a
version of preservationism without implications about degrees of
justification still stands (Goldman 2016).



But this version of preservationism still has other troubles. For one,
it is at best an incomplete account of our justification from memory
(Salvaggio 2018). Memory appears to be reconstructive, generating new
content. And we often believe this new content. If any belief from
memory in new content is justified, preservationism doesn't say
how. It only explains how a preexisting belief can be justified.
Another trouble is this. Preservationism allows that a belief that
*p* can be justified now for a subject who has forgotten her
original justifying evidence for *p*, and who has no other
support for *p*. But suppose the subject learns something that
discredits her original but forgotten evidence (Frise 2017b). Is her
belief that *p* still justified? If so, then preservationism
allows an odd *grandfathering* of past justification; recently
defeated evidence can't justify now, but old justification from
recently defeated evidence remains. But if her belief that *p*
is no longer justified, then preserved justification can disappear
from seemingly arbitrary learning. A subject can lose justification
for her belief that *p* by learning something unimportant to
*p* or to her evidence for *p*.


## 3. Justification and Beyond



This section continues to explore memory's relationship to
justification and other epistemic goods. It does so by touching on
memory's relationship to testimony, the extended mind,
metacognition, knowledge-how, forgetting, and skepticism.


### 3.1 Testimony and Memory



Memory may have a special connection to testimony (see entry on
 epistemological problems of testimony).
 There is debate about whether the two have similar epistemic
functions (Burge 1993; Lackey 2005; Malmgren 2006). Supposing they do,
it is a further question what those functions are. Perhaps neither
generates knowledge or certain other epistemic goods (Audi 1997). It
could be that a speaker's testimony can pass on knowledge to a
hearer, but cannot create knowledge for the hearer when the speaker
lacks it. In a way, testimony is not a foundational source of
knowledge or justification. If preservationism (as anti-generativism)
is true, memory is not a source either. Or, perhaps both can generate
knowledge. Or, perhaps memory and testimony simply have distinct
epistemic functions.



Another possible connection: memory is a kind of testimony.
Specifically, memory may merely be testimony to your current self from
your past self. Remembering is like reading your own diary. Your
justification for believing what you seem to remember depends on your
background justification for trusting your prior judgments and
trusting memory to indicate these judgments. This parallels a simple
view about justification from testimony. Your justification for
believing someone's testimony depends on your background
justification for trusting what the testifier believes and trusting
this person's testimony to indicate her beliefs.



The diary view of memory may be wrong. It fits poorly with cases in
which a subject recalls two beliefs that originally were unequal in
justification but does not recall her original reasons for these
beliefs. The diary view of memory here counts the beliefs as equally
justified. So it must contend that the reasons for the beliefs have
changed, even when it is stipulated that the subject has neither
learned nor forgotten anything relevant. The diary view incorrectly
treats some testimony from your former self equally (Barnett 2015).
Here's another reason to doubt that memory is a kind of
testimony. When memory reports *p*, this is evidence that
*p*, rather than evidence about what memory reports (Weatherson
2015). But when a testifier reports *p*, this isn't
evidence that *p*, but rather evidence about what the testifier
reports.



It could be that memory has a special connection to testimony, but one
that is problematic. Sometimes a subject experiences an event, and
afterwards hears misleading testimony about the event. The subject may
later incorporate the content of that testimony when constructively
recollecting the event, and for that reason form a false belief about
the event. This is the much-discussed "misinformation
effect" (Loftus 1979 [1996]). Less discussed is the
"information effect". Here, the subject hears accurate
testimony about an event she has witnessed, and that testimony shapes
how she later reconstructively recollects the event, leading to a true
belief. Although the belief is accurate, it's accuracy may be
due to a kind of luck that prevents knowledge; at best this is a
"Gettier case" (see entry on
 the analysis of knowledge).
 Michaelian (2013) argues that when the information effect occurs, not
only does memory's reliability increase, but knowledge is also
still possible. The information effect does not involve
*problematic* luck. According to Shanton (2011), constructive
recollection in general is unreliable and leads to false belief in a
nearby possible world. But she suggests it is more plausible that this
recollection can still yield knowledge, than that knowledge requires
either reliability or no false belief in close worlds.


### 3.2 Extended Mind



Cognitive processing may not be limited to biological
brain-processing. It may extend also to artifacts inside the skull, or
even outside. A subject's notebook, for example, may be a part
of his cognitive processing, in the way his memory is part of his
cognitive processing (Clark & Chalmers 1998). Information stored
in the notebook can be part of the subject's dispositional
memory knowledge (Carter & Kallestrup 2016). The subject does not
instead merely relearn the information upon accessing it. Knowledge
may not only extend to memory technology, but this knowledge may in
ways be better than knowledge from biomemory (Carter 2018; Heersmink
& Carter 2020). It may for example be more stable and less
effortful to maintain. Michaelian (2012a), however, argues that an
important case for the extended cognition hypothesis fails. The case
highlights functional similarity between biomemory and alleged memory
that is external to the subject's body. The case specifically
has to do with their similar, purely preservative functioning. But,
Michaelian argues, biomemory lacks this function, so alleged external
memory is not relevantly similar to biomemory after all. Notably, the
view that biomemory has a purely preservative function has in part
motivated views about its epistemic powers, such as both versions of
preservationism.


### 3.3 Metacognition



We are not only cognitively active creatures, but we also monitor and
control our own cognitive activity, typically unreflectively. This
monitoring and controlling is *metacognition*. Memory involves
metacognition (Arango-Munoz 2013, 2014; Arango-Munoz
& Michaelian 2014; Michaelian 2012b; Proust 2013). Thanks to
memory we retrieve information, but then we also evaluate it and our
own retrieval of it. For example the information may not indicate its
origin, and we use heuristics to determine a probable
one--experience as opposed to, say, imagination. We also monitor
how quickly or slowly we retrieve the information, and our epistemic
feelings toward it (such as, say, a feeling of knowing). An
endorsement mechanism controls for example whether we continue or
cease to seek from memory the desired information.



Michaelian (2012b) argues that the metacognitive endorsement mechanism
is reliable and justifying despite its relying on sources of
information that do not always deliver accurate information.
Michaelian (2012c) argues that metacognitive monitoring helps
one's own memory to function reliably, yet that monitoring
testifiers for untrustworthiness is unimportant to testimony's
reliability. Proust (2013) thinks metacognition helps us have
justification, but contends that internalism about epistemic
justification struggles to explain how this is so. Frise (2018c)
argues that metacognition in memory supports a kind of internalism
about epistemic justification over process reliabilism.


### 3.4 Knowledge-How



This entry has discussed memory and knowledge, but only one type of
knowledge. The type is knowledge-that, or propositional knowledge.
What is known here is, or has the form of, a proposition. Maria knows
that the 49ers should have won Super Bowl LIV, and this is
propositional knowledge, or knowledge-that. Another type of knowledge
is knowledge-how (see entry on
 knowledge how).
 Maria knows how to throw a football. This is knowledge-how.



There is much discussion of how these two types of knowledge relate. A
standard view is that they are importantly distinct types. A
controversial view, however, is that knowledge-how consists in or
requires knowledge-that. This view is *intellectualism*. The
philosophy and psychology of memory might shed light on how the two
types of knowledge relate. There is evidence that the two types rely
on distinct memory systems (Michaelian 2011c). Not all knowledge-how
involves knowledge-that. Thus, intellectualism appears false.
Additionally, memory for how to execute physical actions, or
*remembering-how*, appears closely related to knowledge-how.
Remembering-how can endure longer than related propositional
knowledge, allowing individuals with dementia to retain certain skills
(Sutton & Williamson 2014). If remembering-how suffices for
knowledge-how, this may be further evidence against intellectualism.
The subject has lost the knowledge-that while keeping the relevant
knowledge-how.


### 3.5 Forgetting



Forgetting is normatively significant. Not only does some of it invite
moral blame (Bernecker 2018), but it is essential to the
epistemological problems of forgotten evidence and forgotten defeat.
But it is not entirely clear what forgetting is. And surprisingly
little work addresses the nature of forgetting. Some forgetting is a
process, other forgetting is a mental state; forgetting might have
different types of content (e.g., a proposition or an event or an
experience); forgetting involves some characteristic relation to its
content that distinguishes it from other processes or states with the
same content; forgetting has some scale, either binary or a further
graded range (Frise 2018b).



It might seem commonsensical that forgetting, whatever it is exactly,
is incompatible with knowing. What you forget, you no longer know. But
perhaps sometimes a subject forgets what she still knows (Moon 2012b;
Pappas 1983, 1987). The forgetting may involve trying but failing to
mentally access previously learned information. The information may be
mentally accessible to the subject via her memory. The subject fails
to access it, however. She still dispositionally knows what
she's forgetting. Other ways of forgetting are harder to square
with knowing. For example, some forgetting involves information being
lost. And it's plausible that a subject does not still know
information that she has lost.



Forgetting appears to be an epistemic defect, in part because some
forgetting appears incompatible with knowing. It would be better not
to forget, because not forgetting would allow for more
knowing. However forgetting might be a feature of a virtuously
functioning memory system (Michaelian 2011a). Not forgetting, or too
little forgetting, would be a problem. The problem wouldn't be
that human memory would run out of storage space, hampering further
learning. Rather, human memory works better by clearing out clutter,
such as learned information we don't care about. Forgetting
allows faster, more reliable recall, and perhaps a greater ratio of
recall for what we do care about.


### 3.6 Skepticism



Memory fails at times, as we have each experienced. As a result, we
might be inclined to inquire into memory's trustworthiness.
Inquiring may be unnecessary for our having justification. Perhaps
memory could provide it as long as there's no reason to doubt
its trustworthiness (Moon 2017). Memory is trustworthy, and finding
this out is additional evidence in favor of what we believe via
memory. But memory still generates or preserves justification prior to
our inquiry.



Or perhaps if memory is to provide justification for a subject, she
must have reason to suppose her memory is trustworthy. It is not
immediately obvious what the relevant trustworthiness consists in. It
may be a matter of memory functioning in a certain way. And this could
be a matter of memory in general being reliable, tending to yield more
true beliefs than false beliefs. A potential reason to suppose memory
is reliable is that to suggest otherwise is, in a way, self-defeating
(Locke 1971). To show memory is unreliable, we'd presumably need
to cite evidence of its failures. But this evidence comes from memory.
So if we show memory is unreliable, it is because memory supported
believing something, namely, its own unreliability. So even if it is
plausible that memory is unreliable, memory supports some
believing.



It might not matter whether memory *in general* is reliable.
Perhaps it just matters whether memory is reliable in the right
circumstances or for a certain range of beliefs, or whether a given
memory system is reliable, or whether a given memory is likely
correct. An inference to the best explanation argument supports the
latter: a given memory, if accurate, can make better sense of why a
subject now experiences what that memory predicts she would experience
(Hasan 2021).



If memory is to justify certain beliefs it might need to be
trustworthy in a different way. It might need to be
*conditionally* reliable. Mere reliability is a matter of a
process tending to yield more true beliefs than false beliefs.
Conditional reliability is a process tending to do this when all
belief inputs are true. Memory processing could be unreliable, yet
conditionally reliable. It tends to yield false beliefs, but not when
the inputs to it (such as past beliefs) are all true. If, as per one
sort of preservationism, memory cannot generate justification, it does
not seem to matter whether memory is reliable simpliciter. It just
matters whether memory is conditionally reliable. Its conditional
reliability would allow memory to preserve the justification of a past
belief, according process reliabilism. Reliability simpliciter does
not matter for whether memory preserves justification. Reliability
simpliciter does matter for whether memory generates new
justification, but preservationism (as anti-generativism) denies
memory can do this.



Inference to the best explanation may also support memory's
conditional reliability. That memory is conditionally reliable is part
of the best explanation of our having doxastic attitudes at all (Frise
& McCain 2021). Suppose memory functions in a way where it
supplies us with doxastic attitudes, such as beliefs. If memory is not
creating all these attitudes anew, it is taking some attitudes as
inputs and later on yielding attitudes as outputs. On the simpler and
better accounts of how memory does this, it minimally changes the
input along the way. If there is no or little relevant change, the
belief output will have the same truth-value as the input, as it might
even have the same content. So when all belief inputs to memory are
true, memory tends to yield true beliefs rather than false beliefs. It
is conditionally reliable.



However, even if memory is trustworthy in all ways that matter, the
typical person may have an importantly flawed view of how some memory
systems work, such that the typical person fails to know via those
memory systems (Frise 2022). For instance, our folk understanding of
episodic memory fails to appreciate its constructive nature. Leaning
on this folk understanding may imperil knowledge of past events from
episodic memory, as it is plausible that a subject cannot know that
*p* if her justification for believing that *p*
essentially depends on a falsehood.



Instead of focusing on memory's trustworthiness, we might focus
on whether a given belief about the past is correct. Russell (1921)
points out that all or nearly all our beliefs about the past could be
false. We might seem to remember various events and facts about what
has occurred. But we might have come to exist just five minutes ago.
The apparent past is misleading. Russell's skeptical hypothesis
is similar to skeptical hypotheses concerning other alleged sources of
knowledge and justification, such as perception. It is no surprise,
then, that many responses to Russell's skeptical hypothesis
parallel responses to skepticism of other sorts (see entry on
 skepticism).