Nagel: Plantinga's Flip-Side

Massimo Pigliucci has written an excellent piece criticizing Plantinga’s theistic arguments, recounted recently in an interview with Gary Gutting on the New York Times “Stone” blog. (See also Helen de Cruz's discussion.) Plantinga’s belief rests, according to himself, not on argument but on “experience.” We have an inborn inclination to believe in God, and like perceptual experience, this is self-validating.  Theism doesn’t rest, for example, on inference to the best explanation. Denying God because science explains so much of what was once attributed to God is like denying the Moon because it is no longer needed to explain lunacy.

Fair enough. I won’t venture to oppose an argument that is credible only if you believe the conclusion. But what of Plantinga’s arguments against atheism? Here is one that will be familiar to most readers. Suppose that materialism and evolution are true. It follows (for present purposes, never mind how) our belief-producing processes will be imperfectly reliable. Given that we have hundreds of independent beliefs, it’s virtually certain that some will be false. This means that our “overall reliability,” i.e. the probability that we have no false beliefs, is “exceedingly low.” “If you accept both materialism and evolution, you have good reason to believe that your belief-producing faculties are not reliable.”

Wait a minute!

What you showed, Professor Plantinga, is that even if your belief processes were highly but not perfectly reliable—even if, for example, two-thirds of our beliefs were true—“overall reliability,” defined as the probability of all of our beliefs being true, is “exceedingly low: something like 0.0004.” True, but surely acknowledging that at least some of my beliefs are false is not “to fall into a total scepticism!” Bracketing the paradox of the preface (“At least one proposition in this book is false”), which Plantinga rightly does not invoke, this doesn’t give us any reason to be sceptical about any particular proposition (except that all of our beliefs are true). In fact, Plantinga seems to concede that our belief-production processes might be reliable.

All this talk about probabilities masks a deeper misunderstanding about explanation in general.  Let me make the point by using Plantinga’s own calculations. Given 2/3 reliability and 100 independent beliefs, he says “the probability that all of a group of beliefs are true” is 0.0004. Still there are 7 billion persons on Earth. So even if we have somewhat more than 100 independent beliefs each—if you exclude beliefs made credible by direct perception, we don’t have all that many independent beliefs—it is not unlikely that somebody on Earth has no false beliefs. Let’s call this person Vlad. Vlad is, at least for now, infallible. Let’s suppose he locks his position in by committing suicide.

Re Vlad: Here is a bad argument. (Since Plantinga’s theism does not rest on argument, I am not going to say he accepts it.)  Vlad achieved infallibility. Given materialism and atheism, it is impossible to understand how he got that way. Introduce divine providence, and it is more comprehensible how Vlad came to be infallible. Thus inference to the best explanation leads us to affirm the existence of God.

This bad argument is the flip side of Plantinga’s. Plantinga rejects the supposed “scepticism” of affirming the truth of all of our beliefs. On this basis, he rejects the materialism and evolutionism that leads to this scepticism. On the flip side, we affirm the unlikelihood of Vlad being right about everything, and posit God as the best explanation of his amazing prescience. The fallacy lies in equivocating between the unlikelihood of Vlad being infallible and the unlikelihood of there being some infallible person.

The flip-side argument is (in effect) Thomas Nagel’s. Given materialist neo-Darwinism, the prior probability of rational consciousness emerging is very small. So its emergence must argue against materialist neo-Darwinism. That’s not right! Tom wins the lottery. Is that a reason to believe in God?

Let’s concede to Nagelian biology that in the preponderance of possible histories, rational consciousness did not emerge. It just so happens that the actual world is one of the very few in which it did. We wouldn’t be debating the point in a world in which it didn’t. In Nagelian biology, consciousness is a singularity. There is no argument to show that it must be made comprehensible. Nagel thinks that we must give credence to a theory that assigns high prior probability to the emergence of consciousness. This is only true if it actually has high prior probability. What is the argument that it does?