A redated post.
A good place to start in making sense of the argument from desire is Peter Kreeft’s formulation.
1) Every natural, innate desire in us corresponds to some real object that can satisfy that desire.
2) But there exists in us a desire which nothing in time, nothing on earth, no creature can satisfy.
3) Therefore there must exist something more than time, earth and creatures, which can satisfy this desire.
4) This something is what people call "God" and "life with God forever."
A good deal of poetry and literature seem to support the second premise. Human beings are deeply dissatisfied even when all of their earthly needs are satisfied. On the face of things, the most difficult premise to defend is 1). How could we, without first knowing that Joy can be satisfied?
Kreeft responds: This is very easy to refute. We can and do come to a knowledge of universal truths, like "all humans are mortal," not by sense experience alone (for we can never sense all humans) but through abstracting the common universal essence or nature of humanity from the few specimens we do experience by our senses. We know that all humans are mortal because humanity, as such, involves mortality, it is the nature of a human being to be mortal; mortality follows necessarily from its having an animal body. We can understand that. We have the power of understanding, or intellectual intuition, or insight, in addition to the mental powers of sensation and calculation, which are the only two the nominalist and empiricist give us. (We share sensation with animals and calculation with computers; where is the distinctively human way of knowing for the empiricist and nominalist?)
But doesn’t this just mean “We just know?” Why shouldn’t natural unsatisfiable desires arise? This difficulty is especially acute when you look at the naturalistic world-view to which theism is opposed. The naturalistic atheist is prepared to accept a substantial amount of absurdity in human existence, at least if it is measured by the standards of expectations conditioned by theism. Consider the following comments by Keith Parsons here.
Bertrand Russell said that a soul’s habitation must be built on a firm foundation of unyielding despair. However, Parsons, in his debate with William Lane Craig, maintained that the despair is a despair from a theistically conditioned set of expectations concerning life’s meaningfulness.
The question I am asking is this: Is there any reason why a nontheist should be surprised that human beings have desires that are doomed to permanent frustration?
John Beversluis, in his critique of Lewis’s apologetics, suggests that in preface to The Pilgrim’s Regress Lewis offers a justification for 1 in the principle that nature does nothing in vain, but then offers no good reason why we should believe that nature does nothing in vain. In fact, it might be argued that the very principle itself presupposes a teleological understanding of the universe that presupposes theism, thus reducing the argument from desire to begging the question.
But I wonder if some version of the principle that nature does nothing in vain might be accepted by both parties in the debate. Beversluis says that the fact that we are hungry is no evidence that food exists, the actual discovery of food is the only thing that would suffice. But if we were to find creatures with, say, sexual desires, but no way of having sex, and which reproduced asexually, wouldn’t that conflict with out expectations? Wouldn’t biologists he shocked to find such a creature? Wouldn’t the existence of sexual desires be evidence that sex was at least possible or surely of some biological use, even if we did not see any actual mates for these creatures? To argue thus we would not need creationism; even evolutionary biologists would have to agree.
In an earlier post I wrote:
Why should we think that a natural desire within us would not exist unless it was satisfiable? Well, let us suppose that God and evolution are the main two explanations for why we have the desires that we have. We can understand easily why we have those desires if God has outfitted us with the desires that we have. These desires are God’s “calling card” whereby He draws us to Himself. But suppose evolution were the explanation, as it would have to be on naturalistic assumptions. It is possible, of course, that these desires should evolve, but should we expect this? Should we not expect that desires that don’t directly promote survival would be shoved out of the way by desires for food, clothing, and shelter, power, and strength, which do us so much more good from an immediate survival standpoint. If we didn’t know better, we should expect this meme to become extinct. On the face of things, we have something that obviously provides Bayesian confirmation for theism. We have something that is very likely on the theistic hypothesis, and perhaps compatible with atheism, but not very likely given atheism.
At least that’s what I’d like to think. But I do know that evolution is not perfectly efficient. If nature does nothing in vain, how do we account for the human appendix, an organ which now has no use other than to get infected and make money for doctors? In one sense, it is something nature did in vain, in that it doesn’t do anything for us now. On the other hand, I am told that it was used by our ancestors to digest raw meat, back before we learned how to cook. Should we expect human creatures in an atheistic world to desire an object that nothing on earth can satisfy?
This is Bayes’ theorem. H is the hypothesis, K is background knowledge and e is the evidence.
p(h/e & k) = p(h/k) x p(e/h & k)/p(e/k)
Suppose we haven’t considered the evidence concerning the human desire for the infinite, and so we consider this data as e. In using Bayes’ theorem, we begin by considering the probability of the hypothesis, in this case theism, on background knowledge alone. To see if the Bayesian argument from desire has any weight at all, let’s assume that we have a person who thinks that theism and atheism are equally likely. Bayesian theorists have tried in vain to find a method of determining objective antecedent probabilities. So let’s assume that p (h/k) = .5. The next question is how probability is the desire evidence to arise if theism is true. It seems that theism gives us a reason to suppose that these desires would be likely to arise in a theistic universe, especially if that universe were a Christian universe. On Christian theism God’s intention in creating humans is to fit them for eternity in God’s presence. As such, it stands to reason that we should find ourselves dissatisfied with worldly satisfactions. Let’s put the likelihood that we should long for the infinite given theism at .9. Now, what is the likelihood that infinite longings should arise on background knowledge alone. This is the hard part. If we don’t know whether theism is true or not, how likely are we to have desires like Lewis is talking about? I wouldn’t say that such desires couldn’t possibly arise in an atheistic world. Even though such desires seem to have limited evolutionary use, they could well be byproducts of features of human existence that do. But how likely would they arise in such a world? So long as the answer is “less likely than in a theistic world,” the presence of these desires confirms theism. Let’s say that, if we don’t know whether theism is true or not, the likelihood that these desires should arise is .7. Plugging these values into Bayes’ theorem, we go from .5 likelihood that theism is true to a .643 likelihood that theism is true. Thus, if these figures are correct, the argument from desire confirms theism.
I can see Bart Ehrman throwing a fit already. And I will admit that I don’t have supreme confidence in this argument. But I can’t help thinking that there must be something to the argument from desire, especially if the argument is presented in Bayesian terms.