Theistic Notebook

May 22, 2011

Plantinga contra evidentialism (part 2)

Filed under: Notes — David P @ 8:42 am
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Plantinga’s Reformed Epistemology bears heavily on the claim that properly basic beliefs are grounded by appropriate conditions.  In the previous post, we looked at some properly basic beliefs, and we found that the (classical) foundationalist criterion (self-evident, incorrigible, or evident to the senses) fails to capture the full range of obviously properly basic beliefs.  It also seems to steer us towards the rocks of self-referential incoherence.  Turning now to belief in God, Plantinga gives examples of circumstances that “call forth belief in God.”  He claims there is a disposition in us to believe certain propositions in these scenarios.  So it appears he is offering some conditions that the theist might accept.  Here are a few of his examples:

  1. Contemplating the beauty or vastness of the universe calls forth a belief that this vast and intricate universe was created by God.
  2. Doing something that is clearly wrong leads me to believe that God disapproves of what I’ve done.
  3. Confession and repentance brings about a feeling of forgiveness accompanied by the belief that God forgives me for what I’ve done.

What is important about these types of beliefs, is that they self-evidently entail that God exists.  So strictly speaking, there is such a person as God (Plantinga’s preferred way of affirming that God exists) is not a properly basic belief; instead, the propositions expressed by 1-3 above are.

Can we just pick and choose properly basic beliefs?

Hopefully by now the answer is apparent.  No!  Just because we jettison the foundationalist criterion (self-evident, incorrigible, or evident to the senses), that doesn’t commit us to accepting all beliefs as properly basic … for instance, the belief that the Great Pumpkin returns every Halloween.  But surely the Reformed Epistemologist must give an account of properly basic belief.  Plantinga demurs.
“Suppose I don’t know of a satisfactory substitute for the criteria proposed by Classical Foundationalism; I am nevertheless entirely within my rights in holding that certain propositions are not properly basic in certain conditions…it would be irrational to take as basic the denial of a proposition that seems self-evident to you.  Similarly, suppose it seems to you that you see a tree; you would then be irrational in taking as basic the proposition that you don’t see a tree, or that there aren’t any trees.  In the same way, even if I don’t know of some illuminating criterion of meaning, I can quite properly declare [a meaningless expression] meaningless.”

But Plantinga does propose a way for us to establish the criterion of proper basicality using induction. We approach the problem by stacking up obvious examples of conditions where beliefs are held in the properly basic way (and of course we need another pile for obvious ones that are not properly basic in certain conditions).  We will then test various hypotheses against these examples to come up with the an appropriate general statement.  But of course, not everyone will agree on what belongs in the stack.  In particular, Christians may have beliefs about God in their stack.  And thus, the Christian needn’t worry about the Great Pumpkin objection if maintains that we are disposed to believe in God but not the Great Pumpkin.  Of course, the atheist will not agree…but Plantinga questions whether this is particularly relevant.  He says that the “Christian community is responsible to its set of examples, not to theirs.”

In summary, Plantinga has argued three basic points:

  1. The foundationalist criterion (self-evident, incorrigible, or evident to the senses) is not a necessary condition for proper basicality.
  2. One who designates belief in God as properly basic needn’t affirm that such a belief is groundless.
  3. Even if we can’t give a full account of the criterion for proper basicality, we needn’t grant that all beliefs are properly basic.  We can work inductively towards a general criterion using a set of obvious examples.

May 13, 2011

Plantinga contra evidentialism (part 1)

Filed under: Notes — David P @ 8:34 pm
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W.K. Clifford once said that, “It is wrong always, everywhere, and for anyone to believe anything upon insufficient evidence.”  To the contrary, Alvin Plantinga famously maintains that one can rationally believe in God without evidence.  In this series, I will take a look at Plantinga’s essay, “The Evidentialist Objection to Theistic Belief” (Religious Experience and Religious Belief, 1986).  A similar argument is given Faith and Rationality: Reason and Belief in God, 1983.

First off, Plantinga defines a properly basic belief as one that can be rightly held without evidence.  Contrary to popular opinion, properly basic beliefs are not gratuitous or groundless (more on this term later); nevertheless, philosophers disagree over what criteria we should apply to these basic beliefs–that is beliefs that don’t rely on other beliefs for their justification–to classify them as properly basic.  Many foundationalists maintain something like this:

(C) p is properly basic for S if and only p is self-evident, incorrigible, or evident to the senses of S.

Unfortunately, Plantinga finds that this claim can’t satisfy its own criteria for being properly basic (it is neither self-evident, incorrigible, or evident to my senses).  In the absence of any arguments in its favor (which themselves would need to rely on properly basic premises), Plantinga concludes that “the classical foundationalist is in self-referential hot water–his own acceptance of the central tenet of his view is irrational by his own standards.”

Next, Plantinga examines three basic beliefs:

(1) I see a tree.
(2) I had breakfast this morning.
(3) That person is angry.

We will focus on (1) for simplicity.  We can see that a certain sort of experience, perhaps alongside other criteria, justifies one in believing the proposition expressed by (1).  Here’s the trick: this belief has some criteria that grounds its justification; however, Plantinga doesn’t take what many of us see as obvious for granted.  He doesn’t consider the experience of seeing a tree as evidence for (1).  But why doesn’t Plantinga take my being appeared to treely as evidence for belief in the proposition I see a tree?  Because we don’t “infer that belief from others…[or accept it] on the basis of other beliefs.”  In other words, we don’t refer to any propositional evidence when justifying our beliefs about (1).  Thus, by Plantinga’s definition the treely appearance grounds the belief in (1) but it is not (propositional) evidence for (1).  A basic belief is grounded if held in the appropriate justifying circumstances.  Plantinga construes properly basic belief as follows:

(4) In condition C, S is justified in taking p as basic.  Of course C will vary with p.

C obviously includes the treely appearance but is that sufficient?  No.  Perhaps I am heavily dosed with hallucinatory drugs and am clearly not justified in holding (1) in the properly basic way under such conditions.  But regardless of the criteria which justifies this belief, this criteria is the “ground of its justification and, by extension, the ground of the belief itself.”  Next we’ll see how this ties in with belief in God.

1 – recall William Lane Craig’s showing versus knowing distinction

April 13, 2011

An Intro to the Philosophy of Religion Ch. 5 (Design Arguments)

Intro to the Philosophy of ReligionThe analogy argument
Hume summarizes this argument well through the words of Cleanthes.

Look round the world: Contemplate the whole and every part of it: You will find it to be nothing but one great machine, subdivided into an infinite number of lesser machines, which again admit of subdivisions, to a degree beyond what human senses and faculties can trace and explain. All these various machines, and even their most minute parts, are adjusted to each other with an accuracy, which ravishes into admiration all men, who have ever contemplated them. The curious adapting of means to ends, throughout all nature, resembles exactly, though it much exceeds, the productions of human contrivance; of human design, thought, wisdom and intelligence. Since therefore the effects resemble each other, we are led to infer, by all the rules of analogy, that the causes also resemble; and that the Author of nature is somewhat similar to the mind of man; though possessed of much larger faculties, proportioned to the grandeur of the work, which he has executed. (Dialogues Concerning Natural Religion, Oxford World’s Classics Ed., p.45)

Rea and Murray reconstruct the basic argument like this:

5.34 The universe is like a machine.
5.35 Machines are typically caused by designers.
5.36 Therefore: the universe is likely caused by a designer.

Then they work there way to an advanced version:

5.37 There is some property P such that (a) some natural object N (or perhaps the cosmos as a whole) has P, (b) many artifacts (watches, for example) have P, and (c) artifacts that have P do so because they are products of design.
5.38 Things that are alike generally have causes or explanations that are alike as well.
5.39 Therefore: it is reasonable to conclude that N has P because it is likewise the product of design.

Analogy arguments are weak because they either define “machine-ness” in a way that begs the question or else have trouble substantiating the claim that all instances of such machine-ness imply a designer.

Inference to the best explanation
“In drawing this conclusion you make an inference to the best among a number of possible available explanations. Arguments of this sort work only when there are no competing explanations.” Under this criterion, Rea and Murray do not find biological design arguments very compelling. Evolutionary theory is a competing explanation that explains apparent design by reference to “workings of an algorithmic natural process, namely, variation and natural selection.”

However, the contemporary debate has shifted from biological design to cosmological design. As cosmologist and atheist Fred Hoyle remarks, “A common-sense interpretation of the facts suggests that a superintellect has monkeyed with physics as well as with chemistry and biology [to create suitable conditions for life]…”[1] Rea and Murray reconstruct the cosmic fine-tuning argument as follows:

5.40 The universe exhibits fine-tuning of a sort that makes it suitable for life.
5.41 The existence of fine-tuning is probable under theism.
5.42 The existence of fine-tuning is highly improbable under atheism.
5.43 Therefore: fine-tuning provides strong evidence in favor of theism over atheism.

Some examples of fine-tuning are listed: the rate of cosmic expansion after the Big Bang, the strength of the nuclear strong force, and the electromagnetic force (particularly its delicate balance with the strong force).

Some objections can be raised against premise 5.42.   One such objections looks at the configuration of constants and forces.  Is it really improbable that these are fine-tuned for life, as opposed to taking some other life prohibiting configuration?  By way of thought experiment, we are told to imagine a dial with ten numbers on it, each taking on a value between zero and nine.  For life to be possible, all ten dials must have the value 5; the odds of this are one in 10 billion. But what about any other random configuration of values on the dials? The probability is still one in 10 billion, and thus life permitting values are no less probable (indeed, equally as likely) than any other set of values.

Rea and Murray give a counterexample (William Lane Craig has used it before as well).   Suppose a friendly poker game is disrupted after one of the players draws royal flushes for ten straight hands.   To his friends’ dismay, John insists that the sequence of hands he drew was no less probable than any other sequence of hands. Why does John’s response fail to satisfy his companions?   Because there are only a few hands that beat all others, and his friends want to know “why he drew an improbable and special series of hands.” In other words, though the probability of drawing the same hand ten times is equi-probable with drawing any other series of hands, the probability of drawing an unbeatable hand (as opposed to a garbage hand) ten times is not.  Likewise, the probability of the constants and forces taking on life permitting values is not equi-probable with life prohibiting values.

A formidable objection to premise 5.42, the multi-verse objection, asserts that a finely tuned universe is improbable on atheism only if there is a single universe. Perhaps there are many universes with varying natural laws, and so it isn’t so unlikely that one of them is life permitting.   Unfortunately there isn’t a any empirical evidence for this claim. Secondly, it isn’t clear (in these speculative multi-verse theories) that the other universes would take on different constants and forces.   Thirdly, whatever the mechanism for generating universes is, that mechanism itself would have to be fine-tuned; indeed, a universe-making machine might require a higher-level of fine-tuning than modern physics can presently appreciate.

[1] Fred Hoyle, “The Universe: Past and Present Reflections,” Engineering and Science (November 1981), p. 12.

April 6, 2011

An Intro to the Philosophy of Religion Ch. 5 (Cosmological Arguments)

Intro to the Philosophy of ReligionDependence version 1:

5.27 Every being is either dependent or self-explaining.
5.28 Not every being can be dependent.
5.29 Therefore, at least one self-explaining being exists (a being which in turn explains the existence of the dependent beings).

This a posteriori argument seeks to establish the existence of a self-explaining being: one that does not depend on something else for its existence.

Infinite Regress and the Principle of Sufficient Reason
The infinite regress objection (IRO) aims at premise 5.28 by advancing the thesis that, while a finite chain of dependent beings requires a self-explaining being, an infinite chain of dependent beings not.  This objection implies an infinitely old universe, a topic one which cosmology continues to vacillate.  Thus one reply to IRO might simply reference the latest evidence for the Big Bang.  But a better, philosophical reply to IRO involves the Principle of Sufficient Reason (PSR):

PSR There must be a sufficient cause, reason, or explanation for the existence of every thing and for every positive fact.

According to PSR, even an infinite chain of dependent beings will leave some fact(s) unexplained.  One example of such a fact: there is something rather than nothing.  Second, the fact that there is an infinite collection of things.  How will defenders of IRO deal with PSR?  Some have replied that these facts actually are explained.  An example is given in which someone has fifteen dollars–ten dollars in one pocket that came from an ATM and five dollars in the other pocket that came from a friend in repayment of a loan.  Now, what if we asked this person to explain why he has fifteen dollars, why does he have some money rather than none at all?  Once he explains where his five dollars and ten dollars came from (individually), there doesn’t appear to be a further explanation required for the fifteen dollars.

Do these examples show that IRO satisfies PSR?  It depends on yet another principle: the external explanations principle: “A set of dependent beings is explained ‘with no explanatory remainder’ when each member of the set has an explanation and at least one member of the set is explained by appeal to something outside the set of dependent beings to be explained.”  In the case of the fifteen dollars, there is an appeal to something outside of the set: the ATM and the loan re-payer.  In the infinite regress objection, this isn’t true, and thus the objection fails to satisfy the PSR.

Objection to PSR
A serious problem with PSR, raised by Leibniz himself, is that the grand totality of all facts (the SUPERFACT) requires an explanation.  But what exactly would count as an explanation for something like a SUPERFACT?  Whatever the explanation, it can’t be a necessary truth; otherwise, the SUPERFACT would obtain in all possible worlds and thus only the actual world will be possible.  What if the SUPERFACT’s explanation is contingent?  Rea and Murray only leave us with the vague notion that “only very special propositions are true in just one world…truths that are true in only one world are hard to think of.”  The only one they can think of is “the world described in the SUPERFACT exists” which can’t itself explain the SUPERFACT.  They conclude that we should reject PSR. [1]

Dependence version 2:
We might try to replace PSR with a weaker principle, such as there can be no independent contingent thing.  Thus the new argument can be construed as follows:

5.30 Every being is either dependent or necessary.
5.28 Not every being can be dependent.
5.29 Therefore: at least one necessary being exists (a being which dependent beings at least partially depend for their existence).

This version is still susceptible to the IRO.  Finally, Rea and Murray consider it “no easy task” to argue that the universe (as a collection) is a contingent thing.

The kalam version
William Lane Craig’s recent work on this version of the argument has attracted attention from philosophers, cosmologists and physicists. [2]

5.31 Whatever begins to exist has a cause of its coming into existence
5.32 The universe began to exist
5.33 Therefore: the universe has a cause for its coming to exist.

The first premise seems obvious but in fact has fostered lively debate.  The second premise is justified both on a priori and a posteriori grounds.  As to the latter, the best cosmological theories (the Big Bang) all posit a universe that began to exist.  As to the former, some philosophers have argued that an actually infinite series of past moments is impossible.

This argument describes the cause-to-universe relationship in an interesting way, because it posits a cause which exists simultaneously with its effect.  This is important because some object to this argument on the grounds that a timeless cause is incoherent. [3]   The best illustration of this (not in the book but from Craig himself in a lecture I heard one) is that of a bowling ball and a pincushion.  The bowling ball causes the pincushion to be indented in a certain fashion.  Now, imagine that the bowling ball and the pin cushion have forever been in this position.  It would not be the case that one event was causing a succeeding event.  Likewise, “Craig argues that God’s causing the universe to come to be could be simultaneous with its coming to be.”  He also concludes that this timeless cause needs to have some kind of personal agency, namely the ability to bring about effects “at will.”  So, Craig thinks this argument gets us to a timeless quasi-personal being that caused the universe to come into existence.  There are numerous objections to this argument that delve deeply into theories of time, causal explanation, infinity, and more. [4]

1 For a more detailed analysis, see Alexander Pruss, The Principle of Sufficient Reason (Cambridge Studies in Philosophy).
2 See William Lane Craig, The Existence of God and the Beginning of the Universe
3 Quentin Smith has devoted much attention to this topic.  Check out his article on Infidels, “The Uncaused Beginning of the Universe” (1988).
4 More online reading on the cosmological argument: Some Recent Progress on the Cosmological Argument, by Alexander Pruss.  A New Look at the Cosmological Argument, by Robert Koons.  A New Cosmological Argument, by Alexander Pruss and Richard Gale.  A new cosmological argument undone, by Michael J. Almeida and Neal D Judisch.  And finally, The Cosmological Argument, by David Oderberg

March 28, 2011

An Intro to the Philosophy of Religion Ch. 5 (Ontological Arguments)

Intro to the Philosophy of ReligionAnselm, Descartes and objections

1. God is the greatest conceivable being.
2. God exists in the understanding.
3. To exist in reality is better than merely to exist in understanding.
4. Thus, if God exists merely in the understanding, then we can conceive of something greater than God, namely a being just like God, but who also exists.
5. But it is impossible to conceive of a being that is greater than the greatest conceivable being.
6. Thus it is impossible that God exists merely in the understanding.
7. Thus God exists in reality as well as in the understanding.
8. Thus God exists.

Rea and Murray find Anselm’s original formulation of this argument, as it appeared in his famous work the Proslogion, to be problematic.  What exactly are we to make of the second premise?  They refer to Descartes’ version of the argument for help, and take notice of his slightly different notion of God as a being containing all perfections rather than Anselm’s greatest conceivable being.  They reconstruct the argument as follows:

1. God is the greatest possible being (GPB).
2. The GPB possesses every perfection that would make a being great.
3. Existence is a perfection that would make a being great.
4. God possesses existence […thus God exists]

Gaunilo of Mamoutier penned a famous objection to Anselm’s argument, entitled “In Defense of a Fool,” where he facetiously replaces “God” with  “Lost Island” as a proof for the existence of the greatest conceivable island; his objection aims to show how Anselm’s argument leads to absurd conclusions.  But does the argument really work when we plug in other greatest conceivable things?  That depend on what makes something the greatest of its kind.  How many miles of beach would the greatest conceivable island have (100, 1,000, 10,000)?  Certain types of perfection (such as the greatest number of miles of beaches) don’t have an intrinsic maximal value, and thus Mamoutier’s objection hasn’t identified a valid candidate for use in Anselm’s argument .  Not so fast though, this objection might cut both ways if some of God’s own great-making properties don’t have an intrinsic maximal value (e.g., God ‘s being perfectly loving).

But is existence a property at all, much less (or should I say much more) a great-making property?  Kant answered in the negative, maintaining that existence is always presupposed for a thing which is propertied (more simply, Kant maintains that “my cat is black” presupposes “my cat exists”). [1]  Murray and Rea don’t see why a precondition (for ascribing other properties) can’t itself be a property.  For example: taking up space is a precondition for having the property of being red, but taking up space is itself a property.  Their response seems reasonable, except that existence is the precondition for all other properties (or so Kant argues).  But this fact alone doesn’t show that existence isn’t itself a property (or at least I can’t see how it does).

The third and most popular, potent objection to this argument is simply that is begs the question; it assumes God exists before in the premises.  After we modify the first premise to avoid this objection, it’s hard to see how we can reach any satisfactory conclusion.  For instance, if the first premise reads “For anything to count as God,  that thing would have to possess existence” we can follow the argument through and see how this is undesirable.  Rea and Murray, and many other philosopher, think the traditional argument fails to avoid this third objection.

The Modal Ontological Argument
A new rendition of this argument has surfaced via recent work in an area of philosophy known as modal logic.  Modal logic deals with possibility and necessity.   Rea and Murray define a possible world as “a comprehensive description of the way the universe might be … the maximally comprehensive description of our universe is the actual world.”  Contingent beings only exists in some possible worlds but not others.  A necessary being, if it exists, would exist in all possible worlds.  A being possesses a property necessarily if it has that property in all (relevant) possible worlds (Plantinga refers to the properties that a person has necessarily as their “essence” ).  For example, Arnold Schwarzenegger is 6 feet tall ascribes a property to Arnold, but Arnold could be 5 feet tall in another possible world.  On the other hand, Arnold Schwarzenegger is a person ascribes a property to Arnold that he holds in all (relevantly) possible worlds.  Having laid the ground for understanding modal logic, the modal ontological argument is presented as follows.

5.20 God is the greatest possible being.
5.21 The greatest possible being is one that possesses all perfections necessarily.
5.22 Necessary existence is a perfection.
5.23 It is possible that the greatest possible being exists.
5.24 If it is possible that the greatest possible being exists, then that being exists necessarily.
5.25 God exists necessarily.
5.26 God exists.

My rough attempt at stating it with a little less precision and a little less jargon:
If we can show that the great possible being exists is true in at least one possible world, then we have shown that God exists.  Why?  Since the greatest possible being would possess all perfections necessarily (see premise 5.21), this means it would have those perfections in every possible world where it exists.  Since necessary existence (that is, existence in all possible worlds) is a perfection, then it follows that the greatest possible beings exists in all possible worlds is true in all possible worlds if true in any possible world.  Since the actual world (the one we live in) is one of those possible worlds, it follows that God exists in the actual world.

Premise 5.23 is susceptible to refutation.  For instance, some philosophical theologians think that the concept of a greatest possible being entails a contradiction, thus disqualifying God from existing in any possible world.  In other words, if a perfect being is shown to be conceptually incoherent, this argument fails.  A more modest critic might simply insist that we withhold judgement on this argument until we have resolved all the apparent contradictions in philosophical theology.  But a rebuttal can be given to both critics here.  Since premise 5.23 asserts the possibility that the greatest possible being exists, then the ontological defender’s response to conceptual incoherence should be to adjust the concept of the greatest possible being to get in line with what is possible.  Does omnipotence and impeccability entail a contradiction?  No problem, just tweak the concept to remove the contradiction.

One final objection to be raised is that necessary existence is impossible (premise 5.22).  Rea and Murray don’t think that any convincing arguments have been offered in this direction. [2]

Alvin Plantinga, in God, Freedom and Evil (1977), proceeds meticulously through the details of Kant’s objections in a section entitled, “The Irrelevance of Kant’s Objection.” Pdf is available here.  Chris Heathwood wrote a reply entitled, “The Relevance of Kant’s Objection.”
2 See Edward Feser’s summary of Plantinga’s ontological argument here.  Also, see William F. Vallicella’s articles on broadly logical necessity (he disagrees with many philosophers who say that conceivabality entails possibility)  as well as A Modal Ontological Argument and an Argument from Evil Compared.

March 22, 2011

An Intro to the Philosophy of Religion, Ch. 4

Intro to the Philosophy of ReligionThe nature of faith
Murray and Rea offer their account of faith as follows:

“…to say that a person S has faith in proposition p is to say that S believes p despite the fact that (a) there are alternatives to p that are compatible with whatever evidence supports S’s belief that p, and b) there is genuine and somewhat weighty evidence in favor of one or more of those alternatives.”

Since they classify faith as a kind of belief, there can be degrees of faith just as there can be degrees of belief (credences).  In addition, their definition of faith implies that faith can be judged as rational or irrational depending on the evidential context.  But what counts as evidence?

Reliabilism and Evidentialism
The evidentialist maintains that the rationality of a religious belief (merely) depends on the degree to which the belief is supported by arguments–in other words, only propositional evidence counts.  On the other hand, the reliabilist maintains that a belief is rationally held when (a) produced by reliable, properly functioning cognitive faculties, and (b) unaccompanied by overriding reasons to deem the belief irrational.  This implies that experiential evidence (e.g., religious experience) can justify a belief under the right conditions.  Properly basic beliefs are ones which can be justified or held without relying on other beliefs; for instance, perceptual belief is held on the basis of perceptual experience.  Likewise, Rea and Murray think that religious experience might justify a religious belief so long as it satisfies the criterion mentioned above.  What kinds of evidence might defeat our confidence in religious experiences?

Religious disagreement
Just as scientific theories explain sensory experience, Rea and Murray construe religious theories as collective attempts to explain religious experience.  A problem comes to light here: while scientific theories enjoy a fair level agreement, most religious theories are quite the opposite.  In light of this disagreement, one might ask some questions:

1. Do religious theories track truth about reality?

2. Are the arguments for any religious positions successful?

3. If not, should religious belief and practice be abandoned?

The religious skeptic generally replies in the negative to the first two questions, but affirms the last one.  Religious pluralism holds that no religion has a weighter share of (religious) truth than the others.  Pluralists maintain that many religions can capture isolated truths about reality, but none of the religions are superior in this sense.  The third view is religious exclusivism.  The exclusivist affirms what the skeptic denies: that religious theories track truth about reality.  He also affirms what the pluralist denies: that there is one objectively true religious narrative.  This doesn’t entail that all religious truths are known with certainty, but merely that we can have substantial knowledge of the truth about spiritual reality, and we can use this knowledge to judge disparate religious views.

Religious diversity poses a problem for exclusivists, and Rea and Murray undertake to show that this problem doesn’t render exclusivism unreasonable.  Putting aside pragmatic reasons for embracing pluralism, they examine how widespread religious disagreement might constitute evidence against exclusivity.  They conclude (as reliabilists) that it depends on whether or not disagreement should cast doubt on the believer’s reliability to judge the facts at hand.[1]  The mere fact of disagreement is insufficient.  Disagreement plus backgrounds beliefs (beliefs about the supernatural, morality, your own memory) work together to determine how heavily the evidence weighs.  Unfortunately, we don’t have adequate background beliefs about “a typical person’s ability to judge religious matters.”  More importantly, Christian background beliefs predict religious diversity.  So, the evidential force of religious diversity might be weakened.  Rea and Murray acknowledge that this only scratches the surface of the debate over exclusivity.

Is atheism irrational?
Alvin Plantinga has fashioned an argument which, if successful, renders atheism irrational.  Imagine that you’ve acquired evidence that your cognitive faculties are completely unreliable.  What should you make of the following proposition?

(R) Your cognitive faculties are reliable.

Well, firstly, you couldn’t have evidence for (R) that hasn’t already assumed (R), since reliable cognitive faculties are a prerequisite for assessing propositions about reliable cognitive faculties.  More importantly, if you have reason to reject (R), on the basis of the evidence you’ve acquired, then now you have a reason to doubt all of your beliefs, including the belief that (R) is true!  Defeating (R) defeats everything … resulting in global skepticism.

Why should we think that atheism gives us evidence of unreliable faculties?  According to Plantinga, evolutionary theory is concerned with survival and reproduction, and doesn’t give a fig for true beliefs.  Thus, conjoining naturalism with evolutionary theory leads us to believe that our cognitive faculties are unreliable.  Why?  The ability to arrive at truth about the world might be (and Plantinga would say is) irrelevant to the function of enabling us to survive and reproduce.  For example, consider a man who wants to die and he believes that the best way to secure death is to run away from tigers and mate frequently with women.  He’ll do just as well as the man who doesn’t want to die, and believes the best way to secure life is the same.  Thus, Plantinga argues that the probability of our faculties being reliable–given evolution and naturalism–is low.  But if so, then the atheist who accepts evolutionary theory and naturalism has a defeater for his belief that naturalism is true … and a defeater for all his other beliefs too.  Rea and Murray suggest that a more modest version of this argument might work: arguing that natural selection might produce some true beliefs, but why should we think our philosophical and religious beliefs are among these? [2]

1 There are “undercutting” and “opposing” defeaters.  It sounds like Rea and Murray are arguing that an undercutting defeater is needed, since presumably there is no opposing defeater for basic beliefs such as my belief that I was at work yesterday morning.  See this article for more information on defeaters.
2 See Plantinga’s paper “Naturalism Defeated.” Stephen Law has been working up a response.  Also, see Fitelson and Sober’s response.

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