I found this brief exchange between Lewis Wolpert and William Lane Craig on Religion to be very interesting:
Craig: On the one hand, I don't think it's true that we should only believe what we have evidence to believe, but then on the other hand, I think there is, in FACT, good evidence for the existence of God.
Commentator: How'd you come to the conclusion that you should believe something you can't actually see evidence for?
Craig: There are many of our most BASIC beliefs for which we have NO scientific evidence. For example...There are many of our most BASIC beliefs for which we have NO scientific evidence. For example.. . . the reality of the past, the existence of the external world, the presence of other minds. All of these are what philosophers call "properly basic beliefs." They are rational beliefs to hold but there's no way you can prove that the world was not created, say, five minutes ago with built in memory traces and food in our stomachs with a breakfast we never ate.
Wolpert: Are you seriously suggesting that the world could have been created before we came in this morning? Come on, you can't be serious!
Craig: I'm saying that there's no way you can prove SCIENTIFICALLY that the past is real, that the universe didn't come into existence five minutes ago with an illusion of age or that other minds exist.
Wolpert: I can't take that...this is philosophical nonsense. I'm sorry.
Commentator: How do we know that other minds exist?
Wolpert: Well, I think you've got another mind. You seem to be rather similar to other human beings. I have no doubts that you have another mind. These aren't BELIEFS. This is a microphone in front of me. This is not a belief. This is about knowledge in the real world.
Craig: I agree that we should believe these things. I think they are rational to believe, but you can't prove them on the basis of evidence.
Wolpert: Well you CAN touch them - I mean you can touch the microphone. There it is.
Craig: Yes, but if you were a brain in a vat of chemicals being stimulated with electrodes by a mad scientist to THINK that you're having the illusion of this microphone in front of you, your experience would be INDISTINGUISHABLE from the experience of an external world. Our belief in the reality of the external world is not a scientific belief. This is a properly BASIC belief. Or, another analogy, if you were a body lying in the matrix as in the film then your experience would be identical with the experience we have so there are all sorts of very FUNDAMENTAL beliefs about the world which we're perfectly rational to entertain but which cannot be justified by the scientific method.
This exchange between the two of them reveals the differences between philosophers and scientists. I understand Craig's arguments, having used them before myself.
The question in Craig's mind is why he needs scientific evidence for God when we believe things that have no scientific evidence either way. For instance,I might be dreaming right now. And Craig is quite right to point these things out.
Wolpert responds as a scientist who speaks about evidence and probability, and I think he's correct to do so.
But here's the rub. While Craig is correct that it's possible that God exists even if there is no evidence, Wolpert is right to ask to see the evidence. While Craig is right about what is possible, Wolpert is right to talk about what's probable. No matter how long Craig wants to talk about what's possible, he still has to present the evidence...the scientific evidence. No matter how long he wants to speak as a philosopher he must eventually speak as a scientist. He still must talk to the scientist about the evidence in the only terms he will accept, and that's the probability of something existing based upon the evidence.
In Craig's defense, if there is no evidence for something either way, then we simply have no way to assess whether or not it exists. He is arguing that we just cannot say either way. The probability factor is equalized.
But come on. Does Craig really think it's probable that his brains are in a mad scientists vat somewhere? To prove something is possible doesn't get us very far, since there are a great many things that are possible that have no plausibilty. How can he assess the claim that green gremilins stabilize the smallest particles of the universe? Possible? Yes. But if he has to resort to what is possible so many times in his arguments, something is indeed lacking when it comes to the evidence for his beliefs. For if the evidence was overwhelming, he would no longer have to talk about what is possible so often. Think about this, and you'll know exactly what I mean.