Naturalism, Evolution, and Self-Defeat
Author(s): Anthony Peressini
Source: International Journal for Philosophy of Religion, Vol. 44, No. 1 (Aug., 1998), pp. 41-51
Published by: Springer
Stable URL: http://www.jstor.org/stable/40036666
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InternationalJournalfor Philosophy of Religion 44: 41-51,1998.
© 1998 KluwerAcademicPublishers. Printed in the Netherlands.
41
Naturalism, evolution, and self-defeat
ANTHONY PERESSINI
MarquetteUniversity,Milwaukee,Wisconsin,USA
In the intriguingfinalchapterof his book WarrantandProperFunction,Alvin
Plantingaarguesthatnaturalism,conjoined with a neo-Darwinianpicture,is
self-defeating.1This argumenthas drawnits fair share of critical response.2
Plantingain turnhas recentlyrespondedin his as yet unpublishedmanuscript
'NaturalismDefeated'. This firstvolley of debatehas helped bring into focus
severalpoints of contentionbetween Plantingaandhis critics, but to date, the
logical structureof the argumenthas not been an element of the discussion.
In this paper I argue that the logical structureof Plantinga'sargumenthas
been misconstrued- that it does not show that naturalismis self-defeating.
I argue furtherthat properlyreconstructed,it fails to make the case for the
(ordinary)defeat of naturalismas well.
1. The argument
At the core of Plantinga'sevolutionaryargumentagainstmetaphysicalnaturalism is the claim that if one accepts naturalism(N) and the contemporary
evolutionaryaccountof how humancognitive faculties have arisen (E), then
it is irrationalto believe that human cognitive faculties are reliable indicators/obtainersof truth(R). This claim is supportedby an argumentthat the
conditionalprobabilityof R on N&E, Pr(R|N&E),is eitherlow or inscrutable.
The remainingsteps in the argumentdeal with the notion of belief defeaters,
which are propositions(defeaters) that, if accepted, rationally force one to
withholdbelief (to some extent) from anotherproposition(defeatee). Plantinga arguesthatthe low/inscrutableprobabilityPr(R|N&E)defeats the belief
thatour cognitive faculties are reliable (R), and this in turndefeats our belief
in naturalismand evolution (N&E) since these beliefs are products of our
putativelyunreliablecognitive faculties. Thus belief in the conjunctionN&E
is self-defeating.The final step in obtainingthe desiredresult thatnaturalism
simpliciteris self-defeatingis to recognize that if naturalismis true, then in
all probabilityso is evolution, since it is the only game in town.3 It will be
helpful to have a schematicrenderingof the reasoning:
42
ANTHONY
PERESSINI
(0) N -> E
(1) Pr(R|N&E)is low/inscrutable
(2) (1) defeats R
(3) (2) defeats N&E
(4) (0) and (3) defeats N,
wherethe entailmentin premise(0) shouldbe interpretedloosely as something
like 'probabilisticcertainty',since strictly speaking,N does not entail E.
Plantinga'scase for premise (1) turnson the idea that, from an evolutionary point of view, what is causally efficacious is not true belief but rather
fitness-enhancingbehavior. Since it is behaviors that are selected in the
evolutionaryprocess, whether the same process would have selected truth
obtaining/preservingcognitive faculties depends in large part on precisely
how beliefs and the rest of the cognitive machineryare relatedto behavior.
The intuitive idea is that if beliefs are causally unrelatedto behavior,then
it would be quite improbablefor truth-preservingbelief machineryto have
evolved; whereas if beliefs are causally related to behavior and if truthin a
belief can somehow cause more fit behavior, then it would be much more
probablethat our cognitive faculties are truthobtaining/preserving.Accordingly, the justificationfor premise(1) involves an exhaustiveexaminationof
how our beliefs might be relatedto our behavior:an estimate of Pr(R|N&E)
can thenbe madebasedon how probableeach of the possible relationshipsare
and how probablethe respectiverelationshiprendersR. In the end Plantinga
concludes that Pr(R|N&E)is either low, or more defensibly, inscrutable.4I
will omit furtherdetail of Plantinga'sdefense of this premise since I will not
in this paperdirectly criticize it.5
The reasoning behind premise (2) is that if one accepts N&E and understandsthe reasoningbehindthe low/inscrutableestimate of Pr(R|N&E),then
one has reason to withhold belief from R, or at least believe it less strongly.
This is precisely how Plantingacharacterizeshis notion of defeat:
D is a defeaterof B for S iff S's noetic structureincludesB andis such that
any humanbeing (1) whose cognitive faculties arefunctioningproperlyin
the relevantrespects, (2) whose noetic structureis N, and (3) who comes
to believe D but nothing else independentof or strongerthan D would
withholdB (or believe it less strongly).6
It is importantto note that whether one believes Pr(R|N&E) to be low or
inscrutable, in either case, one has a reason to doubt (or not affirm)R, and
hence has a defeaterfor it.
While formally appearingmuch the same as premise (2), premise (3) is
actuallyconsiderablymore complicated.It is in premise (3) thattrulyunique
aspects of Plantinga's argumentemerge. The defeat of N&E embodied in
NATURALISM,EVOLUTION,AND SELF-DEFEAT
43
premise (3) is comprehensive- not only is N&E itself defeated,but so are all
possible defeatersof its defeat. As Plantingapresentsit:
... I have a defeaterfor R. Now of course defeaterscan be themselves
defeated . . . can the defeaterthe naturalisthas for R be defeated?It could
be defeatedonly by something- an argument,for example, that involves
some otherbelief (perhapsas premise).But any such belief will be subject
to the very same defeateras R is. So this defeatercan't be defeated
But if I have an undefeated defeater for R, then by the same token I
have an undefeateddefeaterfor any otherbelief B my cognitive faculties
produce, a reason to be doubtful of that belief, a reason to withhold it.
For any such belief will be producedby cognitive faculties that I cannot
rationallybelieve to be reliable. But then clearly the same will be true
for any propositionthey produce:the fact that I can't rationallybelieve
that the faculties that produce that belief are reliable, gives me a reason
for rejectingthe belief. So the devotee of N&E has a defeaterfor just any
belief he holds - a defeater,as I put it, that is ultimatelyundefeated.But
this means, then, that he ultimately has an undefeateddefeaterfor N&E
itself. And that means that the conjunctionof naturalismwith evolution
is self-defeating,such that one can't rationallyaccept it.7
The defeat of R from premise(2) is being used to serve two ends: the subject
cannotbelieve any propositionsthe potentiallyunreliablefaculties produce;
hence it (a) ensuresthat the defeat of R remainsundefeatedsince any belief
producedthat could serve as a defeat defeateris alreadydefeated, and it (b)
defeats N&E, since it too, as one of the beliefs held, is defeated.
Finally,premise(4) pulls things together.Steps (l)-(3) constitutethe argument thatthe conjunctionN&E is defeated.Thus if one acceptsN simpliciter,
by (0) one must, on pain of probabilisticinconsistency,8accept E and hence
accept N&E; then steps (l>-(3) show that N&E is thereby defeated, and at
last, again on pain of probabilisticinconsistency,it follows from premise (0)
that one must accept N simpliciteras defeated.
2. A initial concern: Partial defeat
I offer the following as a concernwith Plantinga'sargument,ratherthana fullblown objection to it. Whetherthis concern constitutes a decisive problem
is not yet clear, though in offering it here I do mean to suggest that it is
of sufficient gravity to require a response on the part of a devotee of the
argument.Also, it will be helpful for my discussion in the next section to
have a specific example of an objection of this nature.
44
ANTHONYPERESSINI
In Plantinga's characterizationof defeat we see that defeat requires the
subjectto either 'withholdbelief or 'believe it less strongly'.Now of course
these are importantlydifferent in that the former suggests that defeat is an
either/orproposition,while the lattermakes it a matterof degree. Plantinga,
in a footnoteto his characterizationquotedabove, clarifieshow he is thinking
aboutdefeat.9He indicatesthathe is thinkingof defeatas essentially a matter
of degree;i.e., thatpartial defeat (believing less strongly)is fundamentaland
thatfull defeat(withholdingbelief) is a special case of partialdefeatinsofaras
withholdingbelief is a special (extreme) case of believing less strongly.My
concern is that, so construed,'defeat' may not be up to the task of defeating
N in any importantsense. In fact, dependingon the natureand strengthof our
warrantfor believing R, its 'defeat' may amountto almost nothing. To see
why, supposefor the momentthatwe have solid independent(of N&E) reason
to believe R (as we certainlydo) andthatwe acceptpremise(1) as 'defeating'
R in the partial sense. It is quite possible then, that given our independent
support,(1) rationallycompels us to believe R less firmlyonly in the slightest
amount.In this case, R's 'defeat' would have virtuallyno effect on ourdegree
of belief in N&E, since the 'defeat's' effect on our degree of belief in R itself
is negligible. Notice that this outcome is especially plausible if Pr(R|N&E)
is inscrutable(as opposed to improbable),since inscrutability(as opposed to
low probability)does nothing to militate against the independentreason we
have for believing R.
Let us returnnow to the issue of whether one has reason to believe R
independentlyof whetherN&E is true. I submit that this is an immanently
reasonablesupposition.We cannotbegin our epistemology from nothing;the
processmuststartsomewhereandwhereit is almostuniversallytakento begin
is with the provisionalacceptance of our cognitive faculties as trustworthy
with respectto the ordinary,common-sense, middle-sizedworld. Plantinga's
epistemologyis no exception;as he has put it, R has initialinternalwarrant.It
is this initialwarrantfor R thatmustbe weighed againstthe more 'theoretical'
considerationsthatPlantingaoffers and thatmay ultimately'defeat' R. Now
if 'defeat' is construedasfull (either/or)defeat there is nothing more to say:
if R is defeated in this sense, we withhold our belief in R and possibly our
belief in N&E as a result.But this is an implausibleaccountof belief revision
- defeat, like belief, admits of degree - this is why Plantingaintroducesthe
notion of partial defeat, which requiresonly thatthe partiallydefeatedbelief
be believed 'less strongly'.
In the case of partial defeat, however, the fact thatR is (partially)defeated,
does not close the case in the same way. That we have reasonto belief R less
stronglymust be weighed against the initial warrantwe have for R, and it is
this equationthatnecessarilycomplicates life for Plantinga.For this requires
NATURALISM,EVOLUTION,AND SELF-DEFEAT
45
us to considerthe actualextentto which R has been defeated;extremepartial
defeatmay be sufficientto really botherus with respectto the statusof R (e.g.,
if our degree of belief was reduced by say 90 percent), but minimal partial
defeat (e.g., reduced by 1/100th of a percent) may very well be within the
range of the normalebb and flow of degree of belief and consequentlywell
below the thresholdat which we (rationally)do not give it a second thought.
While it may or may not turn out that this concern will constitute an
insurmountableproblem for the argument,I will set it aside in considering
the logical structureof the argument.I note it, however, as an unresolved
issue and will referback to it in the next section.
3. The main problem: Self-defeat
As mentionedabove, a truly unique aspect of Plantinga'sargumentis that it
purportsto show thatN is self-defeatingin a very comprehensiveway, i.e., it
itself containsthe seeds of its own defeat andthe defeat all possible defeaters
of its defeat. The key step here is from (2) to (3) and it is this step that I will
argueis trulyproblematic.
At first glance, this reasoning might appear to be, as Plantinga puts it,
'self-referentiallyincoherent'.Since the subjecteventuallyreaches the point
of ponderingthe rejection of the reliability of his/her cognitive system, and
as Plantingahimself puts it, that seems to call into doubt all of the subject's
beliefs; this then calls into doubtthe defeat of R as well since it too is a belief
(or at least based on beliefs). It seems thatin generalto arguenot-R based on
some reasoningX is to necessarilyundercutthe reasoningX, which in the end
leaves one withoutan argumentfor not-R. Thus an argumentfor rejectingR
is self-defeating,since it is defeatedby its own reasoning,which falls within
its scope.
Plantingadefends his argumentagainst a version of this self-defeating,
self-referentialcriticism by presentingand respondingto what he calls the
'Dreaded Loop Objection'.10This objection makes use of the following
(diachronic)reasoning:
... he believes N&E and sees that this gives him a defeater for R; so he
stops believing N&E; but then he loses his defeater for N&E and R; so
presumablythose beliefs then come flooding back. But then once again
he has a defeater for them, and withholds them; and so on, round and
roundthe loop.11
This objection is distinct from the one I have indicated above since it is
diachronic,whereas the version I offered is synchronic. But as part of his
reply to the Dreaded Loop Objection, Plantingaactually argues for a shift
46
ANTHONY PERESSINI
to a synchronicunderstanding.He rightly points out that rationalitywould
seem to require not getting into this (diachronic)loop; rather,the rational
subject would recognize the (synchronic) structure- the infinite series of
potentialdefeatersanddefeatees. A rationalsubjectwould not get drawninto
the diachronicvortex; the subject would apprehendthe synchronic logical
structureandreasonbased on this. But what is the correctconclusionto make
here?Plantingawrites that
the centralpoint here ... is that the devotee of N&E has a defeater for
N&E at any time at which he believes thatproposition,and sees thatR is
improbableor inscrutablewith respectto N&E, so thatif he believes N&E
he has a reason for withholding any of the beliefs he accepts, including
N&E itself. He has such a defeaterfor N&E even if at that time he also
has a defeaterfor that defeater.His problem,after all, is that N&E gives
him a defeaterfor everythinghe believes.12
What we have then is a series of defeated defeaters, and Plantingaclaims
victory based on this structure.13How plausible is this claim? In order to
discernthis we need to evaluate the logical structureitself.
In his response to the Dreaded Loop Objection, Plantingabacks off his
claim, originally stated in Warrantand Proper Function, that this structure
(viewed synchronically)yields an ultimatelyundefeateddefeaterfor N&E.14
Instead, he points out, that we have a series of defeaterswhich are always
defeated, and whose defeatersare defeated, ad infinitum.15This seems quite
right: it is a mistake to conclude that in such a structurethere is an ultimately undefeateddefeater for N&E; but then what are we to conclude? Is
this (synchronic)series of defeated defeatersdefeating for N&E? Plantinga
suggests that it is, but this is far from clear.Notice firstthat this infinite synchronicstructure,which is a consequenceof takingtoo seriously (pretending
we accept) the possibility that R is doubtful, is an intractablemess. There
is no nonarbitraryway of sorting out 'who wins'. To see this, consider the
following two observationsabout the synchroniclooping structure:
(a) at any level on which the subject believes N&E, the subject has a
defeaterfor N&E, and
(b) at no level does the subjecthave an undefeateddefeaterfor N&E.
Each of these true statementsare just the sort of considerationwe look for
in order to justify (respectively) the following two claims concerning the
outcome of the synchronicloop:
(a7)N&E is defeated since it cannot be rationally accepted without
acceptinga defeaterfor it.
(b') N&E is not defeated since there is no undefeateddefeaterfor it.
NATURALISM,EVOLUTION,AND SELF-DEFEAT
47
This is a predicament:we have two mutuallycontradictory(contrary)claims
(a' and b') each of which arejustified by an appropriateand true observation
(a andb). Plantingaoffers us no non-arbitraryreasonto thinkthat(a) is more
germanethan(b) and hence that (a') is true and (b') is false. What is more, it
seems doubtfulthat there is a non-arbitraryreason to privilege one of (a) or
(b) - as considerationof logically similarproblemswill suggest.
Forexample,the structureof the predicamentis reminiscentof the 'counting
to infinityproblem'. Could I count to infinity if I were to live indefinitely?
On one handwe might answerin the affirmative,since for any naturalnumber
you can name there will be a time at which I count it; but on the otherhand
we might be inclined to deny this, because there is no time at which all the
(natural)numbershave been counted.16The problemis the same:we have no
clear,non-arbitraryway to decide between two contrarybut well-supported
answers to the question. Another similar problem arises in attemptingto
Such
define the sum of an alternatinginfinite series like l+(-l)+l+(-l)
a series can be rearrangedto have any numberof distinct sums there is no
non-arbitraryway to define its sum and so the series is not assigned a sum;it
is said to 'diverge'.17This seems the properresponse to the infinite series of
defeateddefeatersas well: accept the questionof whetherN&E is ultimately
defeatedby this synchronic series as undecidable.It seems sensible then to
step back and reconsiderwhat it was thatbroughtus to this impasse.
As I mentionedabove, what seems to give rise to the problematicseries of
defeateddefeatersis 'taking too seriously' the possibility that R is defeated.
Recall how Plantingatreatsthe defeat of R: he plunges on aheadto see what
follows fromthis defeat. Of course,tryingto determinewhatfollows fromthe
defeatof R is not in itself a problem;in fact, this is preciselywhatI will attempt
to do below. There are, however, importantlydifferentways of considering
what 'follows' from the defeat of R, and it seems thatPlantinga'sapproachis
mistakenin a way that leads to the problematicmorassof defeateddefeaters.
ThatPlantinga'sapproachdoes lead to the impassedescribedabove is reason
in itself to question it, but I believe there is further independentreason to
thinkit mistaken.
The mistakelies in Plantinga'sattemptto determinewhat follows from the
defeatof Rfrom withinthe very system whose coherencyhas been called into
doubtby the defeat of R. To continue on 'deducing' results in such a system
is unhelpful:quite predictablyeverythinggoes hay-wire, since R and hence
the system itself cannotbe trusted.To argue,as Plantingadoes, thatsince R is
doubtfulso is ourjustificationfor N&E, andconsequentlyN&E itself, is to do
just this. This is not a telling result, since as we have seen the same reasoning
may be appliedto anything- includingour reason for thinkingthat N&E is
doubtful.Reasoningin this way is muchlike unearthingan inconsistencyin a
48
ANTHONY PERESSINI
formalsystem andthengoing on to deducefromit one's own pet propositions,
(e.g., 'the Packerswill win the SuperBowl', or 'naturalismis irrational').In
both cases this move is misguided:in the inconsistentsystem it is misguided
becauseany propositionwhatsoevercan be deducedin an inconsistentsystem;
andin the settingof Plantinga'sargument,it is misguidedbecauseeverybelief
is suspect (defeated)if R is suspect (defeated).
The comparisonwith the inconsistent system is helpful also in illustrating an alternativeway of thinking about the defeat of R. What a logician
would do, as many have done, including most notablyFrege, afterdiscovering/demonstratingan inconsistencywithinhis/hersystem is 'step backout' of
the system to the meta-theoreticlevel in orderto considerprecisely how the
inconsistency came about and determinethe most sensible course to pursue
(which axioms to revise) in orderto be rid of it. I proposethat, in a like way,
the reasonableway to respondto R's defeat is to 'step back out' of the system
and determinewhat it was that led to the problematicresult and what it is
that needs to be revised in orderto be rid of it. We are at this point then: we
have discoveredthatour system of beliefs, if they containN&E, entail thatR
is doubtful,and this consequence is unacceptablebecause it is in some sense
(probabilisticor otherwise)inconsistentwith otherof our beliefs.
One might be temptedhere to jump to the conclusion that what Plantinga
has given us is something like what is variously referredto as a proof by
contradiction,or an indirectproof, or a reductioad absurdumwhose ultimate
conclusion is that N&E is false. This conclusion, however, is too fast. The
Quine/Duhemhypothesis is helpful in illustratingwhy. The Quine/Duhem
hypothesispointsout thatphysical theoriesentailobservationalconsequences
only in conjunctionwith a set of backgroundassumptions.18At its core, is the
insight that recalcitrantresults (i.e., a result that contradictswhat is known,
or contradictswhat is observed, or is itself internallycontradictory)do not
follow fromsingle propositions;ratherit takesa moresubstantialcollection of
propositionsto entailthe unhappyresult.A corollaryof this is thatrecalcitrant
results do not logically force one to give up any particularproposition;any
one (or more) of the propositions in the collection that jointly entail the
recalcitrantresultmay be revised in orderto be rid of the result.Withrespect
to the issue at hand, the simple but profoundmoral is that in orderto avoid
R's defeat we are not forced to give up N&E; instead,we have a whole host
of backgroundassumptionsthat play an essential role in entailing that R is
defeatedand any one (or more) of these may droppedin orderto preventthe
entailment.
Some of the backgroundassumptionsnecessaryfor the entailmentinclude,
for example,beliefs concerningthe relationshipof behaviorto mentalcontent;
the nature of the evolutionary process responsible for our cognitive facul-
NATURALISM,EVOLUTION,AND SELF-DEFEAT
49
ties; generalandparticularfactorsgoverningprobabilityandprobabilityestimates; the relationshipof probabilityassignmentsto believing/withholding,
the natureof defeat, warrant,and evidence in general;and the natureof our
particularevidence for/againstR, N, and E. Let B denote the conjunctionof
these backgroundbeliefs. The challenge for the advocateof Plantinga'sargumentcan be statedas follows: supposingthatthe conjunctionN&E&Bentails
that R is highly improbableand hence that R is defeated, it remainsunclear
which among N, E, andthe vast multitudeof beliefs thatmakeup B it is most
rational to revise in orderto avoid the problematicentailment.19Plantinga
has not given us reason to be more doubtfulof N&E thanwe have for being
doubtfulof some of the more thornybackgroundassumptionsinvolved.20
For example, the partialdefeat concern of section II provides a specific
example of a backgroundassumptionthat it might be sensible to reject in
orderto avoid the entailmentthat R is doubtful:it might plausibly turn out
that it makes more sense to be doubtful of the degree of belief calculations
involved in (intuitively) 'computing' the degree to which R was defeated
by Pr(R|N&E&B) being inscrutable and the subsequent degree to which
this defeat of R makes us believe N&E less strongly. Other examples of
potentially problematicbackgroundassumptions include, for example, (a)
'intuitions' concerningthe relevantprobabilitiesthat go into the estimate of
Pr(R|N&E&B),(b) the idea thata low probabilitynecessarilyrendersa belief
irrational,(c) our understandingthe notion of prior probabilitiesand even of
probabilityitself, (d) our understandingof mentality and its relationshipto
the world, and (e) our understandingof the details of evolutionaryprocesses.
To this point I have arguedonly that the structureof the case againstN&E
is not the straightforwardself-defeating structurethat has been suggested,
and that properlyconstrued,Plantinga'sreductiohas at the most established
only thatthe conjunctionN&E&B is defeated.In particular,Plantingahas not
given us any more reason to reject N&E than any other of the assumptions
thathelp entail the defeatof R. A naturalresponseto this mightbe thatunless
I show that something in B is more doubtful than N&E, then N&E stands
as defeated. This is not right, however. It would be right if Plantingahad
given us this argument(to not N&E&B) and had given us furtherreason to
doubt N&E (and not B), but this is clearly not what he has done, nor even
intendedto do. Plantingadid not intendto do this because, if N&E had been
self-defeatingin the way he suggested (mistakenlyas I have argued),then he
would not have needed to get into such issues - this is partof the beauty of a
self-defeatingstructure.We must be carefulnot be undulyswayed by the fact
that in the presentationof the argument,N&E was given the lead role - as
if to suggest that it single-handedlyentailed the 'absurdity',but as we have
seen this ignores the essentialrole played by B.
50
ANTHONY
PERESSINI
If I am right about the structureof Plantinga's considerationsand if in
the end we are uncertainas to whetherparts of B are more or less doubtful
thanN&E, then N&E has not been defeatedby Plantinga'sconsiderations.A
person who held N&E based on some initial provisionalgroundswould not
necessarily be rationallycompelled to give it up in this case merely because
of Plantinga'sreductio:it would dependon the much more complicatedcasespecific comparative epistemic support enjoyed by N&E and the various
conjuncts that make up B. (I note again that the agent might have been so
compelled to give up N&E had N&E in fact turnedout to be self-defeating.)
Thus Plantinga'sconsiderationsdo not go far enough to defeat N&E.
Concluding remarks
I have argued that even granting that Pr(R|N&E) is low/inscrutable,it is
doubtfulthat this itself rendersrationalthe rejectionof N&E, and it certainly does not follow in the way Plantinga suggests. In particular,I hope to
have shown that Plantingahas not given us reason to believe that N itself
is self-defeating. Consequently,if ultimately we reject N based in part on
the Pr(R|N&E)being low/inscrutable,it will be for the logically more mundane but far more complicatedreasonsinvolving the evidentialrelationships
between N, E, R, and the relevantbackgroundassumptionsB.
Acknowledgments
I am gratefulto Alvin Plantinga,James Beilby, LarryMasek, and an anonymous referee for this journalfor helpful conversation,suggestions,and comments.
Notes
1. Alvin Plantinga,Warrantand ProperFunction (Oxford:OxfordUniversityPress, 1993).
2. N. M. L. Nathan, 'Naturalismand self-defeat: Plantinga's version', Religious Studies
33 (1997): 135-142. Evan Fales, 'Plantinga's case against naturalisticepistemology',
Philosophyof Science 63 (1996): 432-45 1. TimothyO'Connor,'An evolutionaryargument
against naturalism?',Canadian Journal of Philosophy 24 (1994): 527-539. J. Wesley
Faith and Philosophy 11 (1994): 255-259.
Robbins, 'Is naturalism-irrational?',
3. 'Naturalismdefeated', p. 13. Warrantand Proper Function, pp. 235-236.
4. 'Naturalismdefeated', pp. 4-13. Warrantand Proper Function, pp. 219-228.
5. For critical work along these lines see Evan Fales, 'Plantinga'scase against naturalized
epistemology', Philosophy of Science 63 (1996): 432-451; also Plantinga's'Naturalism
defeated' contains referencesto forthcomingcritical works.
ANDSELF-DEFEAT
EVOLUTION,
NATURALISM,
51
6. 'Naturalismdefeated', p. 32. Warrantand Proper Function, op. cit., pp. 40-42. See also
the appendixof Plantinga'sWarrant:The CurrentDebate (New York:Oxford University
Press, 1993).
7. 'Naturalismdefeated', p. 12. Warrantand ProperFunction, op. cit., p. 231.
8. In assessing the coherenceof a system, logical consistencyis too course-graineda requirement:one may have a consistent system thatis still highly incoherentbecause some of the
beliefs entail that other of the beliefs are highly improbable(as opposed to impossible).
In other words, given that I believe p, q, and r, iip&q entail not-r, then this is a logical
inconsistency,whereas if p&q entail that the probabilityof r is almost zero, then this is a
probabilisticinconsistency.
9. 'Naturalismdefeated , p. 32, note 40. See also Warrantand Proper Function (p. 41 ff.)
for remarkssuggesting thatdefeat, like beliefs, comes in degrees.
10. 'Naturalismdefeated , pp. 15-16, 53-56. Warrantand Proper t unction, op. cit., p. 234
ff. James Beilby, 'Is evolutionarynaturalismself-defeating?',InternationalJournalfor
Philosophy of Religion 42 (1997): 69-78, has defended the argumentagainst a different
versionof the chargeof self-referentialincoherence.While I thinkwhathe says is probably
right, it does not speak to the issue I am consideringhere.
11. 'Naturalismdefeated', p. 53. Warrantand Proper Function, op. cit., pp. 234-235.
12. 'Naturalismdefeated', p. 56.
13. Note that in the above quotation Plantinga has moved back into diachronic wording; I
assume this is merely a slip and will interprethis responsesynchronically.
14. Warrantand Proper Function, op. cit., p. 235.
15. 'Naturalismdefeated , p. 53.
16. For a discussion of this problem see Fred Dretske s Counting to infinity , Analysis 25
(1964-65): 99-101.
17. For details see, for example, WatsonFulks' AdvancedCalculus (New York:John Wiley
& Sons, 3rd edn., 1978), pp. 486-490.
18. PierreDuhem, TheAim and Structureof Physical Theory,translatedby Philip P. Wiener.
(Princeton,NJ: Princeton University Press [1906] 1954), W. V. Quine, From a Logical
Point of View(Cambridge,MA: HarvardUniversityPress, 2 nd edn., 1961).
19. Plantingatouches ever so briefly on this problem of how to identify which belief it is
rationalto revised given recalcitrantresults in 'Naturalismdefeated' (pp. 33-34). Unfortunately,his discussion is limited to the point thatprecisely which belief is defeated by D
is relative to the subject's 'noetic structure'(system of backgroundbeliefs) and he gives
a simplified example to illustrate that changing backgroundbeliefs may change what
belief(s) it is rationalto revise. Well enough, but what is lacking is enough detail to allow
us to ascertainwhich belief it is rational to revise (take to be defeated) by a particular
"noetic structure"when the structureis rich and complicatedas is the case here.
20. Thingsmay actuallybe even morecomplicated,since each of N andE themselves aremost
plausibly seen as conjunctionsof propositionsany one (or more) of which it is certainly
possible, and may even be rationalto revise in orderto be rid of the entailment.
Addressfor correspondence: AnthonyF. Peressini,Departmentof Philosophy,CoughlinHall
125, MarquetteUniversity,Milwaukee,WI 53201-1881, USA
Phone: (414) 288-5683; Fax: (414) 288-3010; E-mail:peressina@marquette.edu