Thursday, November 17, 2011

What, No Tooth Fairy?

When I started reading Oppy, I was interested in two things: (1) what he considered good arguments from the atheist side, and (2) what he thought was wrong or unconvincing about atheistic arguments. In contrast to Swinburne, Oppy sets a high standard for a good argument: he is only interested in arguments that are, or ought to be, rationally compelling to someone of the opposite persuasion. And he doesn't think any theistic arguments are compelling, so that saves half my work.

Oppy has strangely little to say about atheistic arguments. He spends a section (3.9) considering Quentin Smith's atheological argument from cosmology. (I don't think Smith's suggestion holds up from the point of view of physics, and Oppy doesn't think it holds up philosophically.) He has a whole chapter on arguments from evil. (I don't find these interesting or convincing, so I'm going to skip them.) And he addresses some general atheological arguments in his opening chapter in a discussion of agnosticism, and (350 pages later!) includes a discussion of Clifford's Principle in his conclusion. Also, in the first chapter, he deals with the Evil God arguments like the one used by Stephen Law in his recent debate with William Lane Craig. Apart from these, he only mentions atheological arguments in passing.

(Oppy states at the beginning of the book that he's not going to consider arguments that claim the very concept of an OCMOG is incoherent. He's saving these for another book.)

So there's no discussion at all of what I think is the strongest point in favor of atheism - what I think of as the Tooth Fairy Argument. The closest he comes to it when he addresses some general principles that the atheist might try to call on in those first and last chapters. Let's take a look.

The atheist might appeal to the principle that

in the absence of any positive evidence for the existence of x's, one is rationally required to believe that there are no x's.
 Oppy claims that this principle is refuted by the lottery paradox. He asks us to consider a lottery in which an infinite number of tickets are sold, and only one ticket wins.

If I believe of each ticket that it won't win, then I shall be obliged to conclude that no ticket will win - that is, I will be obliged to believe something false.

According to Oppy, the existence of god(s) is like the lottery: we know that some existence proposition must be true, but since there are infinitely many such propositions (no god, god 1, god 2, etc) there is only an infinitesimal chance of any one of them being true. So the agnostic is justified in rejecting the "no god" hypothesis along with all the others.

Now, this is a very strange argument for Oppy to make, because it relies on making probability statements about an infinite set of possibilities. The problem is simply not mathematically well-defined. Elsewhere (in his chapter on fine tuning) Oppy shows himself to have a very sophisticated understanding of the difficulties of such statements. But here, without batting an eye, he allows the agnostic to cite the lottery paradox as if it were unproblematic.

He concludes his one-paragraph discussion like this:

Thus, for example, although there is no good reason to think that there are currently intelligent beings inhabiting the fifth planet of the Vega system, the correct view to have is simply that this claim is a very unlikely one.
 That is, (complete) lack of evidence is not enough to make us disbelieve in something, it is only enough to make that something very unlikely

I think this is correct in a strictly logical sense, as far as it goes. But I also think it doesn't go far enough. It's not just that we are lacking in evidence for a god, it's that we have positive reasons to believe that something like a god can't possibly exist. Rather than "intelligent life on Vega 5," the analogy should be "purple elephants on the planet Pluto." We know elephants can't exist on Pluto, because mammals need food, oxygen, and liquid water, and none of that is available there.

Likewise for gods. It's not just that we're lacking evidence for them: we have good reason to think that intelligence requires a complex neural system (or something like it - as in a computer). The evidence is both experimental and theoretical. Experimentally, all known intelligent beings have complex neural systems. And theoretically, the ability to process information requires some such system.

But according to theists, God doesn't have any neurons. He doesn't have a material body at all. In fact, the OCMOG has no moving parts. How then, can God be intelligent?

Gods are as unlikely as purple Plutonian pachyderms.

Saturday, November 12, 2011

Why Change Your Mind?

Suppose I have some belief. Under what circumstances should I change it?

A common atheist response is that we should reject any belief for which we don't have evidence.  Graham Oppy calls this "Clifford's principle." Oppy thinks it's untenable.

Oppy starts off his book with a discusion of beliefs and their formation and revision. He approves of Harman's Principle of Conservatism:

One is justified in continuing to fully accept something in the absence of special reason not to.

Specifically, Harman says I shouldn't change my mind simply because my belief is not adequately justified (denial of the Principle of Negative Undermining). But I should change my mind if I have positive reasons for thinking my belief is no good (the Principle of Positive Undermining).

Oppy doesn't go into great detail on these principles, but I think what he is getting at is something like the following. We each have a complex network of interlocking beliefs. Many of these beliefs have never been critically examined (by me), and hence aren't adequately justified. For example, I believe Minsk is a city in Russia. I have never been to Russia, let alone Minsk, nor have I ever met anyone from there. I probably learned about Minsk from a book or a casual conversation, or possibly in school. According to Oppy, I should go on believing this, even though I do not have adequate justification. If someone comes along and says, "Minsk isn't in Russia, you idiot, it's the capital of Belarus!" or if I bother to look it up in an atlas, then I have reason to change my belief.

Most of our beliefs are like this. I believe a squirrel is a mammal, even though I have never seen one suckle its young. I believe water is composed of hydrogen and oxygen, even though I have never performed an experiment to prove this. I believe my father was born in Philadelphia, even though I have never seen his birth certificate. And so forth.

In this view, the atheist who says, "I never believe anything unless I have evidence for it" is saying something profoundly stupid. Such a principle would require a retreat to near total skepticism.

Oppy's position here is a sophisticated version of the religionist who says, "But you have faith, too!" And I think he's right. If "faith" means "belief without adequate supporting reasons," then we all have to have faith. Life is simply too short to completely, or even adequately, examine all of our beliefs.

This helps us understand why so many people have irrational beliefs, and why they are so hard to change. It is actually better (in an evolutionary sense) to continue to believe unsupported things than to jettison too many beliefs and be paralyzed into inaction. It may be that something like the Principle of Conservatism is built into our psychological makeup to prevent this kind of paralysis.

Thursday, November 10, 2011

Arguing About Gods

Graham Oppy's book, Arguing About Gods, is an odd one. Oppy, an atheist, says his aim is to survey the arguments for and against the existence of an "orthodoxly conceived monotheistic god," which I'm going to call OCMOG for short. He says right at the outset that he thinks it is not irrational to be theist, agnostic, or atheist. Not surprisingly, by the end of the book he has concluded that there are no really convincing arguments either for or against OCMOG.

Oppy spends most of the book on arguments for OCMOG. These he ably dismantles. (Anyone planning on debating William Lane Craig ought to memorize this book.) Why, then, does he think it is not irrational for a theist to remain theist or an agnostic to remain agnostic? The basic idea is that people start from different "priors" and have access to different evidence, so it is by no means surprising that they will come to different, and even incompatible, beliefs. And they can do so in a completely rational manner. (Not that they always do, of course.)
A rational agent will persist with the views she has until she is shown that she can improve her view by changing it.
So the question for the atheist is whether he has arguments that are rationally compelling to the theist, just as the question for the theist is whether he has arguments that are rationally compelling to the atheist. And Oppy thinks the answer is "no."

Although I agree that people can differ without being irrational, and I am willing to entertain the idea that that might even be true about the existence of God, I think Oppy sets the bar for rationality too low. I wonder if he would insist that astrology believers, UFO enthusiasts, and Bigfoot hunters make no mistakes of rationality.

Friday, November 4, 2011

The Resurrection of Jesus

Keith Parsons has a post up on Secular Web responding to Stephen T. Davis's review of the book The Empty Tomb, to which Parsons contributed an essay. Parsons uses a lot of nice examples from recent history to illustrate how bizarre beliefs form and spread. He notes:

... aspects of the history of the Second World War are debated vigorously, sometimes fiercely, even though the events are massively documented and occurred within the living memory of millions of people. Often the only honest thing to say is that the evidence is compatible with various hypotheses. A fortiori we should be very circumspect in our conjectures about what happened nearly 2000 years ago in obscure circumstances.

Parsons mentions the hallucination hypothesis for the resurrection appearances (though he doesn't claim it is the only, or even the best, explanation).  I have often felt that there is an even simpler explanation, that comes right out of the Bible:

13 Now that same day two of them were going to a village called Emmaus, about seven miles[a] from Jerusalem. 14 They were talking with each other about everything that had happened. 15 As they talked and discussed these things with each other, Jesus himself came up and walked along with them; 16 but they were kept from recognizing him.
 17 He asked them, “What are you discussing together as you walk along?”
   They stood still, their faces downcast. 18 One of them, named Cleopas, asked him, “Are you the only one visiting Jerusalem who does not know the things that have happened there in these days?”
   19 “What things?” he asked.
   “About Jesus of Nazareth,” they replied.....

 25 He said to them, “How foolish you are, and how slow to believe all that the prophets have spoken! 26 Did not the Messiah have to suffer these things and then enter his glory?” 27 And beginning with Moses and all the Prophets, he explained to them what was said in all the Scriptures concerning himself.
 28 As they approached the village to which they were going, Jesus continued on as if he were going farther. 29 But they urged him strongly, “Stay with us, for it is nearly evening; the day is almost over.” So he went in to stay with them.
 30 When he was at the table with them, he took bread, gave thanks, broke it and began to give it to them. 31 Then their eyes were opened and they recognized him, and he disappeared from their sight. 32 They asked each other, “Were not our hearts burning within us while he talked with us on the road and opened the Scriptures to us?”

Now, if you discount the idea that this was actually Jesus and the magical disappearance, this all seems very reasonable. Two followers were walking along and discussing Jesus's death (not implausible). They met a traveling rabbi who didn't look like Jesus (not implausible). They told him they were discussing the Messiah, and the rabbi began explaining the messianic interpretation of various scripture passages (not implausible). Later on, they reflected on this conversation and decided it was Jesus himself who had met them. This last step might strike some as implausible, but I think if there were already stories of Jesus's appearance circulating, it would actually be quite psychologically reasonable.

In this scenario we see how, without any dreams, hallucinations, or weird psychological experiences, Jesus's followers could come to believe that Jesus had "appeared" to them. This explanation might not work for all of the appearance stories, because it relies on the disciples having a predisposition to interpret experiences in terms of appearances of Jesus. Perhaps the first "appearance" was a dream or something. But it might help explain how, once the resurrection meme was in place, it spread so widely. We don't need to posit mass hallucinations, just people re-interpreting their very ordinary experiences in extraordinary terms.