Aron Lucas

A family of theistic arguments contends that the human ability to reason is to be expected under theism, but is surprising under metaphysical naturalism, and thus provides evidence favoring theism over naturalism. One common line of argument is that unguided evolution favors traits that aid in survival and reproduction, rather than traits conducive to discovering the truth. Thus, evolutionary naturalism provides us with no reason to expect our cognitive faculties to be reliable, whereas theism does provide us with reason to believe that God would have created human beings with cognitive faculties aimed at discovering the truth. Several naturalists have responded with arguments that there is in fact significant survival and reproductive value in having accurate cognitive faculties, but in this paper Aron Lucas takes a different tact. Namely, Lucas argues that even if the general fact that human beings can reason favors theism over naturalism, nevertheless the more specific fact that human reasoning suffers from a variety of cognitive biases favors naturalism over theism. If this is right, then arguments from reason can only be deemed successful by understating the full extent of our knowledge concerning human reasoning, thereby committing what Paul Draper has called the fallacy of understated evidence. After fully outlining the available data concerning human reasoning, Lucas concludes that the existence of human cognitive biases does not merely neutralize the evidential significance of the human ability to reason, but in fact overpowers it, tipping the scales in favor of naturalism (all else held equal).

In Hume's Abject Failure, philosopher John Earman argues that David Hume's famous maxim that no testimony is sufficient to establish that a miracle has occurred unless its falsehood would be more miraculous than the miracle itself is just a trivial tautology, namely that we should not believe a miracle claim unless the evidence makes it more probable than not. But even if this interpretation is correct, contemporary Christian apologists fail to satisfy Hume's purportedly obvious condition that it must be more probable that a miracle occurred than that it did not occur when they argue that the miraculous resurrection of Jesus probably occurred.

If the values of the physical constants of our universe were even slightly different, life could not exist. Some have argued that the fact that life does exist thus provides strong evidence that God fine-tuned these values to allow life to emerge. According to the fine-tuning argument, the existence of a life-permitting universe is very improbable on naturalism, but not so on theism. However, we have no way of determining the probability or improbability of actualizing a life-permitting universe on naturalism, for we can only compare our universe against the infinitesimally small subset of other possible universes that have the same physical laws—not the infinite set of all other possible universes.

The key premise of the fine-tuning argument for the existence of God is the alleged improbability of the physical constants taking on values that fall within the narrow life-friendly range. In this paper Aron Lucas examines whether this improbability alone is enough to ground a successful theistic argument from design. He concludes that the fine-tuning proponent is impaled on the horns of a trilemma: he can either reject the argument for having a false premise, reject it for being circular, or accept it at the cost of rejecting the moral argument for the existence of God.