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).
Reppert argues that the existence of human reason gives us good reason to suppose that God exists. If the world were as the materialist supposes, then we would be unable to reason to this conclusion. This contention is often challenged by the claim that mental and physical explanations can be given for the same event. But a close examination of the question of explanatory compatibility reveals that the sort of explanation that would have to be given for the events of inferring that atheism is true, for example, is incompatible with the event being explicable as a purely physical product of a physical universe.
"In C. S. Lewis's Dangerous Idea: In Defense of the Argument from Reason (InterVarsity: 2003), Victor Reppert has contributed what is surely the most extensive defense of the so-called 'Argument from Reason' yet to appear in print. In this critique, I will point out what I believe are the most important conceptual flaws in his arguments, and explain in detail how his arguments are ineffective against my own personal worldview."
C. S. Lewis's argument from reason (AfR) claims that the process of inference by which consideration of premises causes us to adopt a conclusion cannot be coherently conceived of in terms of physical cause-and-effect alone. In C. S. Lewis's Dangerous Idea, Victor Reppert maintains that the argument still poses a strong challenge to naturalism. However, Richard Carrier has attempted to refute Reppert's version of the AfR by invoking developments in cognitive science and computational theory. In this essay Darek Barefoot argues that advances in cognitive science do not affect the AfR since there is an absolute conceptual divide between rational mental causes and physical computational ones. Furthermore, if the AfR is successful, it reveals that rationality is fundamental to the universe, not simply a by-product of physical cause-and-effect; and this, in turn, is readily explicable on theism, but problematic for naturalism.