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## 1. Abduction: The General Idea
You happen to know that Tim and Harry have recently had a terrible row
that ended their friendship. Now someone tells you that she just saw
Tim and Harry jogging together. The best explanation for this that you
can think of is that they made up. You conclude that they are friends
ag... |
empty carton of milk. You conclude
that one of your house-mates got up at night to make him- or herself a
midnight snack and was too tired to clear the table. This, you think,
best explains the scene you are facing. To be sure, it might be that
someone burgled the house and took the time to have a bite while on
the job... |
trike you as
providing much more contrived explanations of the data than the one
you infer to.
Walking along the beach, you see what looks like a picture of Winston
Churchill in the sand. It could be that, as in the opening pages of
Hilary Putnam's book *Reason, Truth, and History*,
(1981), what you see is actually ... |
d. That, in any case, is what you come away believing.
In these examples, the conclusions do not follow logically from the
premises. For instance, it does not follow logically that Tim and
Harry are friends again from the premises that they had a terrible row
which ended their friendship and that they have just been... |
s, terrible rows, and joggers that
might warrant an inference from the information that you have about
Tim and Harry to the conclusion that they are friends again, or even
to the conclusion that, probably (or with a certain probability), they
are friends again. What leads you to the conclusion, and what
according to a ... |
they have just been seen jogging together. (The proviso that
a hypothesis be true if it is to explain anything is taken as read
from here on.) Similar remarks apply to the other two examples. The
type of inference exhibited here is called *abduction* or,
somewhat more commonly nowadays, *Inference to the Best*
*Explana... |
e
distinction between deduction, on the one hand, and induction and
abduction, on the other hand, corresponds to the distinction between
necessary and non-necessary inferences. In deductive inferences, what
is inferred is *necessarily* true if the premises from which it
is inferred are true; that is, the truth of the p... |
nce, *a* is a *B*.
>
But not all inferences are of this variety. Consider, for instance,
the inference of "John is rich" from "John lives in
Chelsea" and "Most people living in Chelsea are
rich." Here, the truth of the first sentence is not guaranteed
(but only made likely) by the joint truth of the second and thir... |
t John is a member of the
minority of non-rich inhabitants of Chelsea. The case is similar
regarding your inference to the conclusion that Tim and Harry are
friends again on the basis of the information that they have been seen
jogging together. Perhaps Tim and Harry are former business partners
who still had some fina... |
d
never to make up.
It is standard practice to group non-necessary inferences into
*inductive* and *abductive* ones. Inductive inferences
form a somewhat heterogeneous class, but for present purposes they may
be characterized as those inferences that are based purely on
statistical data, such as observed frequencies... |
nd
> French.
>
>
> Louise is a Flemish college student.
>
>
> Hence, Louise speaks both Dutch and French.
>
However, the relevant statistical information may also be more vaguely
given, as in the premise, "Most people living in Chelsea are
rich." (There is much discussion about whether the conclusion of
an ... |
th Dutch and
French--or whether it can *sometimes* be stated in
qualitative terms--for instance, if the probability that it is
true is high enough--and sometimes not. On these and other issues
related to induction, see Kyburg 1990 (Ch. 4). It should also be
mentioned that Harman (1965) conceives induction as a special ... |
y have observed many
gray elephants and no non-gray ones, and infer from this that all
elephants are gray, *because that would* *provide the best
explanation for why you have observed so many gray elephants*
*and no non-gray ones*. This would be an instance of an
abductive inference. It suggests that the best way to di... |
re non-necessary inferences), but
in abduction there is an implicit or explicit appeal to explanatory
considerations, whereas in induction there is not; in induction, there
is *only* an appeal to observed frequencies or statistics. (I
emphasize "only," because in abduction there may also be
an appeal to frequencies or ... |
city*, meaning
that it may be possible to infer abductively certain conclusions from
a *subset* of a set *S* of premises which cannot be
inferred abductively from *S* as a whole. For instance, adding
the premise that Tim and Harry are former business partners who still
have some financial matters to discuss, to the pre... |
se--the last two premises alone
do warrant that inference. The reason is that what counts as the best
explanation of Tim and Harry's jogging together in light of the
original premises may no longer do so once the information has been
added that they are former business partners with financial matters to
discuss.
### ... |
as psychologists tend to agree that abduction is
frequently employed in everyday reasoning. Sometimes our reliance on
abductive reasoning is quite obvious and explicit. But in some daily
practices, it may be so routine and automatic that it easily goes
unnoticed. A case in point may be our trust in other people's
test... |
n Adler (1994, 274f),
"[t]he best explanation for why the informant asserts that
*P* is normally that ... he believes it for duly responsible
reasons and ... he intends that I shall believe it too,"
which is why we are normally justified in trusting the
informant's testimony. This may well be correct, even though in
co... |
ther, possibly
even more fundamental, role of abduction in linguistic practice, to
wit, its role in determining what a speaker means by an utterance.
Specifically, it has been argued that decoding utterances is a matter
of inferring the best explanation of why someone said what he or she
said in the context in which th... |
the best explanation of a speaker's utterance
whenever the semantic content of the utterance is insufficiently
informative for the purposes of the conversation, or is too
informative, or off-topic, or implausible, or otherwise odd or
inappropriate; see, for instance, Bach and Harnish 1979 (92f), Dascal
1979 (167), and... |
t limited to everyday contexts. Quite the
contrary: philosophers of science have argued that abduction is a
cornerstone of scientific methodology; see, for instance, Boyd 1981,
1984, Harre 1986, 1988, Lipton 1991, 2004, and Psillos 1999.
According to Timothy Williamson (2007), "[t]he abductive
methodology is the best s... |
mples.
At the beginning of the nineteenth century, it was discovered that the
orbit of Uranus, one of the seven planets known at the time, departed
from the orbit as predicted on the basis of Isaac Newton's
theory of universal gravitation and the auxiliary assumption that
there were no further planets in the solar s... |
ery good explanation. Two astronomers, John
Couch Adams and Urbain Leverrier, instead suggested (independently of
each other but almost simultaneously) that there was an eighth, as yet
undiscovered planet in the solar system; that, they thought, provided
the best explanation of Uranus' deviating orbit. Not much later,
... |
physicist Joseph John
Thomson. Thomson had conducted experiments on cathode rays in order to
determine whether they are streams of charged particles. He concluded
that they are indeed, reasoning as follows:
>
>
> As the cathode rays carry a charge of negative electricity, are
> deflected by an electrostatic force... |
path of these rays, I can see no escape from the conclusion
> that they are charges of negative electricity carried by particles of
> matter. (Thomson, cited in Achinstein 2001, 17)
>
>
>
The conclusion that cathode rays consist of negatively charged
particles does not follow logically from the reported experimen... |
n is the best--in
this case presumably even the only plausible--explanation of his
results that he could think of.
Many other examples of scientific uses of abduction have been
discussed in the literature; see, for instance, Harre 1986,
1988 and Lipton 1991, 2004. Abduction is also said to be the
predominant mode of... |
nescu 2016 on abductive reasoning in the context of
medicine).
Last but not least, abduction plays a central role in some important
philosophical debates. See Shalkowski 2010 on the place of abduction
in metaphysics (also Bigelow 2010), Krzyzanowska, Wenmackers, and
Douven 2014 and Douven 2016a for a possible role o... |
ilosophical role
in epistemology and in the philosophy of science, where it is
frequently invoked in objections to so-called underdetermination
arguments. Underdetermination arguments generally start from the
premise that a number of given hypotheses are empirically equivalent,
which their authors take to mean that the... |
d in believing any particular one of the
hypotheses. (This is rough, but it will do for present purposes; see
Douven 2008 and Stanford 2009, for more detailed accounts of
underdetermination arguments.) A famous instance of this type of
argument is the Cartesian argument for global skepticism, according to
which the hyp... |
an
evil demon, or that we are brains in a vat, connected to a
supercomputer; see, e.g., Folina 2016). Similar arguments have been
given in support of scientific antirealism, according to which it will
never be warranted for us to choose between empirically equivalent
rivals concerning what underlies the observable part... |
ions, for instance, by defining the notion strictly in terms
of hypotheses' making the same predictions. Those responding
then argue that even if some hypotheses make exactly the same
predictions, one of them may still be a better explanation of the
phenomena predicted. Thus, if explanatory considerations have a role
i... |
uth, or
some such, depending--as will be seen below--on the version
of abduction one assumes) of one of a number of hypotheses that all
make the same predictions. Following Bertrand Russell (1912, Ch. 2),
many epistemologists have invoked abduction in arguing against
Cartesian skepticism, their key claim being that eve... |
ly good explanations of what they predict;
in particular, the skeptical hypotheses have been said to be
considerably less simple than the "ordinary world"
hypothesis. See, among many others, Harman 1973 (Chs. 8 and 11),
Goldman 1988 (205), Moser 1989 (161), and Vogel 1990, 2005; see
Pargetter 1984 for an abductive resp... |
rentz's version of the aether theory. For even
though these theories make the same predictions, the former is
explanatorily superior to the latter. (Most arguments that have been
given for this claim come down to the contention that Special
Relativity Theory is ontologically more parsimonious than its
competitor, which... |
Lorentz's.)
## 2. Explicating Abduction
Precise statements of what abduction amounts to are rare in the
literature on abduction. (Peirce did propose an at least fairly
precise statement; but, as explained in the supplement to this entry,
it does not capture what most nowadays understand by abduction.) Its
core id... |
ver, these
formulations are slogans at best, and it takes little effort to see
that they can be cashed out in a great variety of prima facie
plausible ways. Here we will consider a number of such possible
explications, starting with what one might term the "textbook
version of abduction," which, as will be seen, is man... |
ring premises encompassing explanatory considerations and
yielding a conclusion that makes some statement about the truth of a
hypothesis. The differences concern the premises that are required, or
what exactly we are allowed to infer from them (or both).
In textbooks on epistemology or the philosophy of science, on... |
at* *H**i*
which best explains *E*.
An observation that is frequently made about this rule, and that
points to a potential problem for it, is that it presupposes the
notions of candidate explanation and best explanation, neither of
which has a straightforward interpretation. While some still hope that
the former can ... |
and
coherence with well-established theories; the best explanation would
then be the hypothesis which, on balance, does best with respect to
these virtues. (See, for instance, Thagard 1978 and McMullin 1996.)
The problem is that none of the said virtues is presently particularly
well understood. (Giere, in Callebaut (e... |
n simplicity and on coherence--for instance, Forster
and Sober 1994, Li and Vitanyi 1997, and Sober 2015, on simplicity and
Bovens and Hartmann 2003 and Olsson 2005, on coherence--the first
part of this claim has become hard to maintain; also, Schupbach and
Sprenger (2011) present an account of explanatory goodness dir... |
s of explanatory goodness and
Koslowski *et al*. 2008, on the role of coherence with
background knowledge in those assessments.)
Furthermore, many of those who think ABD1 is headed along the right
lines believe that it is too strong. Some think that abduction
warrants an inference only to the *probable* truth of the... |
e*
*approximate* truth.
The real problem with ABD1 runs deeper than this, however. Because
abduction is ampliative--as explained earlier--it will not
be a sound rule of inference in the strict logical sense, however
abduction is explicated exactly. It can still be *reliable* in
that it mostly leads to a true conclus... |
rue, then *H* is true as well
(or *H* is approximately true, or probably true, or probably
approximately true). But this would not be *enough* for ABD1 to
be reliable. For ABD1 takes as its premise only that some hypothesis
is the best explanation of the evidence *as compared to other
hypotheses in a* *given set*. Thus... |
comparison with any other hypotheses that we might
have conceived (but for lack of time or ingenuity, or for some other
reason, did not conceive). In other words, it must hold that at least
typically the *absolutely* best explanation of the evidence is
to be found among the candidate explanations we have come up with,... |
t at all, presumably. To believe otherwise, we must
assume some sort of privilege on our part to the effect that when we
consider possible explanations of the data, we are somehow predisposed
to hit, inter alia, upon the absolutely best explanation of those
data. After all, hardly ever will we have considered, or will ... |
n response to this, one might argue that the challenge to show that
the best explanation is always or mostly among the hypotheses
considered can be met without having to assume some form of privilege
(see Schupbach 2014 for a different response, and see Dellsen
2017 for discussion). For given the hypotheses we have man... |
e to conceive. Then
simply define *H*n+1 := !*H*1
[?] ... [?] !*H**n* and add this new
hypothesis as a further candidate explanation to the ones we already
have. Obviously, the set
{*H*1,...,*H*n+1} is exhaustive,
in that one of its elements must be true. Following this in itself
simple procedure would seem enough to m... |
y hypotheses
*H**j* that imply *H*n+1 and, had
they been formulated, would have been evaluated as being a better
explanation for the data than the best explanation among the candidate
explanations we started out with, *H*n+1 itself will
in general be hardly informative; in fact, in general it will not even
be clear wha... |
above proposal, we may add to our candidate explanations that neither
of these two theories is true. But surely this further hypothesis will
be ranked quite low *qua* explanation--if it will be
ranked at all, which seems doubtful, given that it is wholly unclear
what its empirical consequences are. This is not to say ... |
A more promising response to the above "argument of the bad
lot" begins with the observation that the argument capitalizes
on a peculiar asymmetry or incongruence in ABD1. The rule gives
license to an absolute conclusion--that a given hypothesis is
true--on the basis of a comparative premise, namely, that that
partic... |
th
"probable truth" or "approximate truth." In
order to avoid it, one has two general options.
The first option is to modify the rule so as to have it require an
absolute premise. For instance, following Alan Musgrave (1988) or
Peter Lipton (1993), one may require the hypothesis whose truth is
inferred to be not onl... |
ce *E* and candidate explanations
*H*1,..., *H**n* of
*E*, infer the truth of *that* *H**i*
which explains *E* best, provided *H**i* is
satisfactory/good enough *qua* explanation.
Needless to say, ABD2 needs supplementing by a criterion for the
satisfactoriness of explanations, or their being good enough, which,
howe... |
usion; this option, too, can in turn be realized in
more than one way. Here is one way to do it, which has been proposed
and defended in the work of Theo Kuipers (e.g., Kuipers 1984, 1992,
2000).
ABD3
Given evidence *E* and candidate explanations
*H*1,..., *H**n* of
*E*, if *H**i* explains *E* better than
any of the... |
are on offer today (see, e.g., Niiniluoto 1998).
One noteworthy feature of the congruous versions of abduction
considered here is that they do not rely on the assumption of an
implausible privilege on the reasoner's part that, we saw, ABD1
implicitly relies on. Another is that if one can be certain that,
however man... |
1 does
(supposing that one would not be certain that no potential explanation
is as good as the best explanation one has thought of if the latter is
not even satisfactory or sufficiently good).
As mentioned, there is widespread agreement that people frequently
rely on abductive reasoning. Which of the above rules *e... |
17, forthcoming)? Philosophical
argumentation is unable to answer these questions. In recent years,
experimental psychologists have started paying attention to the role
humans give to explanatory considerations in reasoning. For instance,
Tania Lombrozo and Nicholas Gwynne (2014) report experiments showing
that *how* a... |
ers to how likely we are to generalise that
property to other classes of things (see also Sloman 1994 and Williams
and Lombrozo 2010). And Igor Douven and Jonah Schupbach (2015a),
(2015b) present experimental evidence to the effect that
people's probability updates tend to be influenced by
explanatory considerations in... |
tory considerations tended to be more accurate, as determined
in terms of a standard scoring rule. (See Lombrozo 2012 and 2016 for
useful overviews of recent experimental work relevant to explanation
and inference.) Douven and Patricia Mirabile (2018) found some
evidence indicating that people rely on something like AB... |
ly
stated rules we *ought* to rely on (if we ought to rely on any
form of abduction), where philosophical argumentation should be able
to help, the situation is hardly any better. In view of the argument
of the bad lot, ABD1 does not look very good. Other arguments against
abduction are claimed to be independent of the... |
scussed below--do not discern between
specific versions. So, supposing people do indeed commonly rely on
abduction, it must be considered an open question as to which
version(s) of abduction they rely on. Equally, supposing it is
rational for people to rely on abduction, it must be considered an
open question as to whi... |
abductive reasoning, it
may still be asked whether this practice is rational. For instance,
experimental studies have shown that when people are able to think of
an explanation for some possible event, they tend to overestimate the
likelihood that this event will actually occur. (See Koehler 1991, for
a survey of some ... |
nations
compared to more complicated ones. Although these studies are not
directly concerned with abduction in any of the forms discussed so
far, they nevertheless suggest that taking into account explanatory
considerations in one's reasoning may not always be for the
better. (It is to be noted that Lombrozo's experime... |
e normative status of
abduction are so far to be found in the philosophical literature. This
section discusses the main criticisms that have been levelled against
abduction, as well as the strongest arguments that have been given in
its defense.
### 3.1 Criticisms
We have already encountered the so-called argument... |
e meant to be more general. The first
even purports to challenge the core idea underlying abduction; the
second is not quite as general, but it is still meant to undermine a
broad class of candidate explications of abduction. Both objections
are due to Bas van Fraassen.
The first objection has as a premise that it i... |
2). The alleged problem then is that it
is "an elementary logical point that a more informative theory
cannot be more likely to be true [and thus] attempts to describe
inductive or evidential support through features that require
information (such as 'Inference to the Best Explanation')
must either contradict themselv... |
clearly the extension has more ways of being
false" (van Fraassen 1985, 280).
It is important to note, however, that in any other kind of case than
the "paradigm" one, the putative elementary point is not
obvious at all. For instance, it is entirely unclear in what sense
Special Relativity Theory "has more ways of b... |
o the latter.
(If van Fraassen were to object that the former is not really more
informative than the latter, or at any rate not more informative in
the appropriate sense--whatever that is--then we should
certainly refuse to grant the premise that in order to be more
explanatory a theory must be more informative.)
T... |
and thus be
redundant, or be at variance with it but then, on the grounds of
Lewis' dynamic Dutch book argument (as reported in Teller 1973),
be probabilistically incoherent, meaning that they may lead one to
assess as fair a number of bets which together ensure a financial
loss, come what may; and, van Fraassen argue... |
(1993) have pointed out, a
loss in one respect may be outweighed by a benefit in another. It
might be, for instance, that some probabilistic version of abduction
does much better, at least in our world, than Bayes' rule, in
that, on average, it approaches the truth faster in the sense that it
is faster in assigning a ... |
discussion). If it does, then following that rule
instead of Bayes' rule may have advantages which perhaps are not
so readily expressed in terms of money yet which should arguably be
taken into account when deciding which rule to go by. It is, in short,
not so clear whether following a probabilistically incoherent rule... |
ering which other epistemic and
decision-theoretic rules are deployed along with it; coherence should
be understood as a property of packages of both epistemic and
decision-theoretic rules, not of epistemic rules (such as
probabilistic rules for belief change) in isolation. In the same
paper, a coherent package of rule... |
aassen's critique of probabilistic versions of
abduction.)
### 3.2 Defenses
Hardly anyone nowadays would want to subscribe to a conception of
truth that posits a necessary connection between explanatory force and
truth--for instance, because it stipulates explanatory
superiority to be necessary for truth. As a res... |
y support the claim that (in some form) abduction
is a reliable rule of inference.
The best-known argument of this sort was developed by Richard Boyd in
the 1980s (see Boyd 1981, 1984, 1985). It starts by underlining the
theory-dependency of scientific methodology, which comprises methods
for designing experiments, ... |
scientists draw heavily on already accepted theories. The
argument next calls attention to the apparent reliability of this
methodology, which, after all, has yielded, and continues to yield,
impressively accurate theories. In particular, by relying on this
methodology, scientists have for some time now been able to f... |
re at least approximately true.
From this and from the fact that these theories were mostly arrived at
by abductive reasoning, he concludes that abduction must be a reliable
rule of inference.
Critics have accused this argument of being circular. Specifically, it
has been said that the argument rests on a premise--t... |
ity of this type of
inference is precisely what is at stake. (See, for instance, Laudan
1981 and Fine 1984.)
To this, Stathis Psillos (1999, Ch. 4) has responded by invoking a
distinction credited to Richard Braithwaite, to wit, the distinction
between premise-circularity and rule-circularity. An argument is
premise... |
is used in
the very same argument. As Psillos urges, Boyd's argument is
rule-circular, but not premise-circular, and rule-circular arguments,
Psillos contends, *need not* be viciously circular (even though
a premise-circular argument is always viciously circular). To be more
precise, in his view, an argument for the re... |
*R*'s reliability.
Psillos claims that in Boyd's argument, this proviso is met. For
while Boyd concludes that the background theories on which scientific
methodology relies are approximately true on the basis of an abductive
step, the use of abduction itself does not guarantee the truth of his
conclusion. After all, g... |
Thus, Psillos concludes, Boyd's argument still
stands.
Even if the use of abduction in Boyd's argument might have led
to the conclusion that abduction is *not* reliable, one may
still have worries about the argument's being rule-circular. For
suppose that some scientific community relied not on abduction but on
a r... |
of this rule mostly would lead to the adoption of very
unsuccessful theories. Nevertheless, the said community might justify
its use of IWE by dint of the following reasoning: "Scientific
theories tend to be hugely unsuccessful. These theories were arrived
at by application of IWE. That IWE is a reliable rule of
infere... |
y application
of IWE, we may conclude that IWE is a reliable rule of
inference." While this would be an utterly absurd conclusion,
the argument leading up to it cannot be convicted of being viciously
circular anymore than Boyd's argument for the reliability of
abduction can (if Psillos is right). It would appear, then,... |
ion about the rule at
issue is not sufficient for such an argument to be valid. A further
necessary condition is "that one should not have reason to doubt
the reliability of the rule--that there is nothing currently
available which can make one distrust the rule" (Psillos 1999,
85). And there is plenty of reason to dou... |
do we really have *no* reason to doubt the
reliability of abduction? Certainly *some* of the abductive
inferences we make lead us to accept *falsehoods*. How many
falsehoods may we accept on the basis of abduction before we can
legitimately begin to distrust this rule? No clear answers have been
given to these questio... |
that it relies on
abduction. But Psillos makes it clear that the point of philosophical
argumentation is not always, and in any case need not be, to convince
an opponent of one's position. Sometimes the point is, more
modestly, to assure or reassure oneself that the position one
endorses, or is tempted to endorse, is ... |
g the rule from within the perspective of
someone who is already sympathetic towards abduction; see Psillos 1999
(89).
There have also been attempts to argue for abduction in a more
straightforward fashion, to wit, via enumerative induction. The common
idea of these attempts is that every newly recorded successful
a... |
duction is a
reliable rule of inference, in the way in which every newly observed
black raven adds some support to the hypothesis that all ravens are
black. Because it does not involve abductive reasoning, this type of
argument is more likely to also appeal to disbelievers in abduction.
See Harre 1986, 1988, Bird 1998 ... |
s firmly
established itself as the dominant view on confirmation; currently one
cannot very well discuss a confirmation-theoretic issue without making
clear whether, and if so why, one's position on that issue
deviates from standard Bayesian thinking. Abduction, in whichever
version, assigns a confirmation-theoretic ro... |
t all to the concept of explanation. Does
this imply that abduction is at loggerheads with the prevailing
doctrine in confirmation theory? Several authors have recently argued
that not only is abduction compatible with Bayesianism, it is a
much-needed supplement to it. The so far fullest defense of this view
has been g... |
, Weisberg 2009, and Poston 2014, Ch. 7; for discussion, see Roche
and Sober 2013, 2014, and McCain and Poston 2014.)
This requires some clarification. For what could it mean for a
Bayesian to be an explanationist? In order to apply Bayes' rule
and determine the probability for *H* after learning *E*,
the Bayesian a... |
*H*; the former two are mostly called "prior
probabilities" (or just "priors") of, respectively,
*H* and *E*, the latter the "likelihood" of
*H* on *E*. (This is the official Bayesian story. Not all of
those who sympathize with Bayesianism adhere to that story. For
instance, according to some it is more reasonable to ... |
hese values? As is well
known, probability theory gives us more probabilities once we have
some; it does not give us probabilities from scratch. Of course, when
*H* implies *E* or the negation of *E*, or when
*H* is a statistical hypothesis that bestows a certain chance on
*E*, then the likelihood follows "analytically... |
t always the case,
and even if it were, there would still be the question of how to
determine the priors. This is where, according to Lipton, abduction
comes in. In his proposal, Bayesians ought to determine their prior
probabilities and, if applicable, likelihoods on the basis of
explanatory considerations.
Exactly... |
rs to assign to a
collection of rival hypotheses and you wish to follow Lipton's
suggestion. How are you to do this? An obvious--though still
somewhat vague--answer may seem to go like this: Whatever exact
priors you are going to assign, you should assign a higher one to the
hypothesis that explains the available data ... |
n, may well assign a prior to the best explanation that
is even higher than the one you assign to that hypothesis. In fact,
his priors for best explanations may even be consistently higher than
yours, not because in his view explanation is somehow related to
confirmation--it is not, he thinks--but, well, just because.
... |
esian
epistemology, priors (and sometimes likelihoods) are up for grabs,
meaning that one assignment of priors is as good as another, provided
both are coherent (that is, they obey the axioms of probability
theory). Lipton's recommendation to the Bayesian to be an
explanationist is meant to be entirely general. But wha... |
it, that is, *lower* his
priors for best explanations? Or rather should he give even
*higher* priors to best explanations than those he already
gives?
Perhaps Lipton's proposal is not intended to address those who
already assign highest priors to best explanations, even if they do so
on grounds that have nothing to... |
dless of one's reasons for assigning those priors. The
answer to the question of how explanatory considerations are to guide
one's choice of priors would then presumably be that one ought
to assign a higher prior to the best explanation than to its rivals,
if this is not what one already does. If it is, one should just... |
ef a person assigns before the receipt of
*any* data. If there are already data in, then, clearly, one
may assign higher priors to hypotheses that best explain the
then-available data. However, one can sensibly speak of "best
explanations" even before any data are known. For example, one
hypothesis may be judged to be ... |
of the others. More generally, such judgments may be based on
what Kosso (1992, 30) calls *internal features* of hypotheses
or theories, that is, features that "can be evaluated without
having to observe the world.")
A more interesting answer to the above question of how explanation is
to guide one's choice of prior... |
sians do not do so, however. These Bayesians
think priors must obey principles beyond the probability axioms in
order to be admissible. Objective Bayesians are divided among
themselves over exactly which further principles are to be obeyed, but
at least for a while they agreed that the Principle of Indifference is
amon... |
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