The Argument from Reason is an argument for the existence of God largely developed by C.S. Lewis who once delivered this compendious formulation of the argument:

“ One absolutely central inconsistency ruins [the popular scientific philosophy]. The whole picture professes to depend on inferences from observed facts. Unless inference is valid, the whole picture disappears... unless Reason is an absolute[,] all is in ruins. Yet those who ask me to believe this world picture also ask me to believe that Reason is simply the unforeseen and unintended by-product of mindless matter at one stage of its endless and aimless becoming. Here is flat contradiction. They ask me at the same moment to accept a conclusion and to discredit the only testimony on which that conclusion can be based." ” —C.S. Lewis, Is Theology Poetry





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The argument Edit

The argument against materialism holds:

For an assertion to be capable of truth or falsehood it must come from a rational source (see explanation below). No merely physical material or combination of merely physical materials constitute a rational source. (i.e. anti-panpsychism) Therefore, no assertion that is true or false can come from a merely physical source. The assertions of human minds are capable of truth or falsehood

Conclusion: Therefore, human minds are not a merely physical source (see explanation below).

The argument for the existence of God holds:

(5) A being requires a rational process to assess the truth or falsehood of a claim (hereinafter, to be convinced by argument).

(6) Therefore, if humans are able to be convinced by argument, their reasoning processes must have a rational source.

(7) Therefore, considering element two above, if humans are able to be convinced by argument, their reasoning processes must have a non-physical (as well as rational) source.

above, if humans are able to be convinced by argument, their reasoning processes must have a non-physical (as well as rational) source. (8) Rationality cannot arise out of non-rationality. That is, no arrangement of non-rational materials creates a rational thing.

(9) No being that begins to exist can be rational except through reliance, ultimately, on a rational being that did not begin to exist. That is, rationality does not arise spontaneously from out of nothing but only from another rationality.

(10) All humans began to exist at some point in time.

(11) Therefore, if humans are able to be convinced by argument, there must be a necessary and rational being on which their rationality ultimately relies.

Conclusion: This being we call God.

Agreeing views by other theist philosophers Edit

Philosophers such as Victor Reppert, William Hasker and Alvin Plantinga have expanded on the so-called "Argument from Reason" and credit C.S. Lewis—who called it "The Cardinal Difficulty of Naturalism," the title of chapter three of the book—with first bringing the argument to light in Miracles.[1]

In short the argument holds that if, as thoroughgoing naturalism entails, all of our thoughts are the effect of a physical cause, then we have no reason for assuming that they are also the consequent of a reasonable ground. Knowledge, however, is apprehended by reasoning from ground to consequent. Therefore, if naturalism were true, there would be no way of knowing it—or anything else not the direct result of a physical cause—and we could not even suppose it, except by a fluke.[1]

By this logic, the statement "I have reason to believe naturalism is valid" is self-referentially incoherent in the same manner as the sentence "One of the words of this sentence does not have the meaning that it appears to have." or the statement "I never tell the truth" [2]. That is, in each case to assume the veracity of the conclusion would eliminate the possibility of valid grounds from which to reach it. To summarize the argument in the book, Lewis quotes J. B. S. Haldane who appeals to a similar line of reasoning:[3]

“ If my mental processes are determined wholly by the motions of atoms in my brain, I have no reason to suppose that my beliefs are true ... and hence I have no reason for supposing my brain to be composed of atoms. ” —J. B. S. Haldane, Possible Worlds, page 209

New York University philosopher Thomas Nagel thinks the argument rules out the coherence of physicalism. He writes in The Last Word[4]:

“ To put it schematically, the claim “Everything is subjective” must be nonsense, for it would itself have to be either subjective or objective. But it can’t be objective, since in that case it would be false if true. And it can’t be subjective, because then it would not rule out any objective claim, including the claim that it is objectively false. ”

Arthur Schopenhauer makes a similar claim in The World as Will and Representation

“ ...materialism is the philosophy of the subject who forgets to take account of himself. ” —Arthur Schopenhauer, The World as Will and Representation, II, Ch. 1

In his essay Is Theology Poetry, Lewis himself summarises the argument in a similar fashion when he writes:

“ “ If minds are wholly dependent on brains, and brains on biochemistry, and biochemistry (in the long run) on the meaningless flux of the atoms, I cannot understand how the thought of those minds should have any more significance than the sound of the wind in the trees. ”

Lewis is frequently credited with bringing the argument to prominence; however a roughly contemporaneous version can be found in G.K. Chesterton's 1908 book Orthodoxy. In the third chapter, entitled "The Suicide of Thought," Chesterton elaborates on a very similar argument. He writes:

“ That peril is that the human intellect is free to destroy itself...It is idle to talk always of the alternative of reason and faith. It is an act of faith to assert that our thoughts have any relation to reality at all. If you are merely a skeptic, you must sooner or later ask yourself the question, "Why should anything go right; even observation and deduction? Why should not good logic be as misleading as bad logic? They are both movements in the brain of a bewildered ape?" ” —G.K. Chesterton, Orthodoxy, page 25[5]

Similarly Chesterton asserts that the argument is a fundamental, if unstated, tenant of Thomism in his book St. Thomas Aquinas: The Dumb Ox

“ Thus, even those who appreciate the metaphysical depth of Thomism in other matters have expressed surprise that he does not deal at all with what many now think the main metaphysical question; whether we can prove that the primary act of recognition of any reality is real. The answer is that St. Thomas recognised instantly, what so many modern sceptics have begun to suspect rather laboriously; that a man must either answer that question in the affirmative, or else never answer any question, never ask any question, never even exist intellectually, to answer or to ask. I suppose it is true in a sense that a man can be a fundamental sceptic, but he cannot be anything else: certainly not even a defender of fundamental scepticism. If a man feels that all the movements of his own mind are meaningless, then his mind is meaningless, and he is meaningless; and it does not mean anything to attempt to discover his meaning. Most fundamental sceptics appear to survive, because they are not consistently sceptical and not at all fundamental. They will first deny everything and then admit something, if for the sake of argument--or often rather of attack without argument. I saw an almost startling example of this essential frivolity in a professor of final scepticism, in a paper the other day. A man wrote to say that he accepted nothing but Solipsism, and added that he had often wondered it was not a more common philosophy. Now Solipsism simply means that a man believes in his own existence, but not in anybody or anything else. And it never struck this simple sophist, that if his philosophy was true, there obviously were no other philosophers to profess it. ” —G.K. Chesterton, St. Thomas Aquinas[6]

The argument is, in effect, one for mind-body dualism. In 21st century philosophic discussion, the argument is closely related to David Chalmers's hard problems of consciousness, Jaegwon Kim and the problem of mental causation, and debates concerning the incompatibility of naturalism and free will.

“ Supposing there was no intelligence behind the universe, no creative mind. In that case, nobody designed my brain for the purpose of thinking. It is merely that when the atoms inside my skull happen, for physical or chemical reasons, to arrange themselves in a certain way, this gives me, as a by-product, the sensation I call thought. But, if so, how can I trust my own thinking to be true? It's like upsetting a milk jug and hoping that the way it splashes itself will give you a map of London. But if I can't trust my own thinking, of course I can't trust the arguments leading to Atheism, and therefore have no reason to be an Atheist, or anything else. Unless I believe in God, I cannot believe in thought: so I can never use thought to disbelieve in God." ” —C.S. Lewis, The Case for Christianity

The original version of Miracles contained a different version of chapter 3 entitled "The Self-Contradiction of the Naturalist." In it, Lewis made virtually the same argument but did not distinguish between physical causes of beliefs and rational grounds of beliefs. He also referred to atomic motions in the brain as "irrational." In a Socratic Club debate, G.E.M. Anscombe criticized this, accusing him of taking advantage of ambiguous meanings of the words "why", "because", and "explanation", which prompted Lewis to revise the chapter. The revised chapter presents a more detailed elucidation of the argument, distinguishing clearly between the causes of beliefs and the grounds of beliefs, and also changing most uses of "irrational" to "non-rational". G.E.M. Anscombe commented on the process after Lewis's death:

“ The fact that Lewis rewrote that chapter, and rewrote it so that it now has those qualities [to meet Anscombe's objections], shows his honesty and seriousness. The meeting of the Socratic Club at which I [i.e. Anscombe] read my paper has been described by several of his friends as a horrible and shocking experience which upset him very much. Neither Dr. Harvard (who had Lewis and me to dinner a few weeks later) nor Professor Jack Bennet remembered any such feelings on Lewis's part [...] My own recollection is that it was an occasion of sober discussion of certain quite definite criticisms, which Lewis's rethinking and rewriting showed he thought was accurate. I am inclined to construe the odd accounts of the matter by some of his friends—who seem not to have been interested in the actual arguments of the subject-matter—as an interesting example of the phenomenon called projection.[7] ”

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