Argument from reason
The argument from reason is a transcendental argument against metaphysical naturalism and for the existence of God. The best-known defender of the argument is C. S. Lewis. Lewis first defended the argument at length in his 1947 book, Miracles: A Preliminary Study. In the second edition of Miracles, Lewis substantially revised and expanded the argument.
Contemporary defenders of the argument from reason include Alvin Plantinga, Victor Reppert and William Hasker.
The argument
is the view that nature as studied by the natural sciences is all that exists. Naturalists deny the existence of supernatural deities, souls, an afterlife, or anything supernatural. Nothing exists outside or beyond the physical universe.The argument from reason seeks to show that naturalism is self-refuting, or otherwise false and indefensible.
According to Lewis,
More precisely, Lewis's argument from reason can be stated as follows:
1. No belief is rationally inferred if it can be fully explained in terms of nonrational causes.
Support: Reasoning requires insight into logical relations. A process of reasoning is rational only if the reasoner sees that Q follows from, or is supported by, P, and accepts Q on that basis. Thus, reasoning is trustworthy only if it involves a special kind of causality, namely, rational insight into logical implication or evidential support. If a bit of reasoning can be fully explained by nonrational causes, such as fibers firing in the brain or a bump on the head, then the reasoning is not reliable, and cannot yield knowledge. Consider this example: Person A refuses to go near the neighbor’s dog because he had a bad childhood experience with dogs. Person B refuses to go near the neighbor’s dog because one month ago he saw it attack someone. Both have given a reason for staying away from the dog, but person A’s reason is the result of nonrational causes, while person B has given an explanation for his behavior following from rational inference. Consider a second example: person A says that he is afraid to climb to the 8th story of a bank building because he and humans in general have a natural fear of heights resulting from the processes of evolution and natural selection. He has given an explanation of his fear, but since his fear results from nonrational causes, his argument does not follow from logical inference.
2. If naturalism is true, then all beliefs can be fully explained in terms of nonrational causes.
Support: Naturalism holds that nature is all that exists, and that all events in nature can in principle be explained without invoking supernatural or other nonnatural causes. Standardly, naturalists claim that all events must have physical causes, and that human thoughts can ultimately be explained in terms of material causes or physical events that are nonrational.
3. Therefore, if naturalism is true, then no belief is rationally inferred.
4. We have good reason to accept naturalism only if it can be rationally inferred from good evidence.
5. Therefore, there is not, and cannot be, good reason to accept naturalism.
In short, naturalism undercuts itself. If naturalism is true, then we cannot sensibly believe it or virtually anything else.
In some versions of the argument from reason, Lewis extends the argument to defend a further conclusion: that human reason depends on an eternal, self-existent rational Being. This extension of the argument from reason states:
1. Since everything in nature can be wholly explained in terms of nonrational causes, human reason must have a source outside of nature.
2. If human reason came from non-reason it would lose all rational credentials and would cease to be reason.
3. So, human reason cannot come from non-reason.
4. So human reason must come from a source outside nature that is itself rational.
5. This supernatural source of reason may itself be dependent on some further source of reason, but a chain of such dependent sources cannot go on forever. Eventually, we must reason back to the existence of eternal, non-dependent source of human reason.
6. Therefore, there exists an eternal, self-existent, rational Being who is the ultimate source of human reason. This Being we call God.
Anscombe's criticism
On 2 February 1948, Oxford philosopher Elizabeth Anscombe read a paper to the Oxford Socratic Club criticizing the version of the argument from reason contained in the third chapter of Lewis's Miracles.Her first criticism was against the use of the word "irrational" by Lewis. Her point was that there is an important difference between irrational causes of belief, such as wishful thinking, and nonrational causes, such as neurons firing in the brain, that do not obviously lead to faulty reasoning. Lewis accepted the criticism and amended the argument, basing it on the concept of nonrational causes of belief.
Anscombe's second criticism questioned the intelligibility of Lewis's intended contrast between "valid" and "invalid" reasoning. She wrote: "What can you mean by 'valid' beyond what would be indicated by the explanation you would give for distinguishing between valid and invalid, and what in the naturalistic hypothesis prevents that explanation from being given and from meaning what it does?" Her point is that it makes no sense to contrast "valid" and "invalid" reasoning unless it is possible for some forms of reasoning to be valid. Lewis later conceded that "valid" was a bad word for what he had in mind. Lewis didn't mean to suggest that if naturalism is true, no arguments can be given in which the conclusions follow logically from the premises. What he meant is that a process of reasoning is "veridical", that is, reliable as a method of pursuing knowledge and truth, only if it cannot be entirely explained by nonrational causes.
Anscombe's third objection was that Lewis failed to distinguish between different senses of the terms "why", "because", and "explanation", and that what counts as a "full" explanation varies by context. In the context of ordinary life, "because he wants a cup of tea" may count as a perfectly satisfactory explanation of why Peter is boiling water. Yet such a purposive explanation would not count as a full explanation in the context of physics or biochemistry. Lewis accepted this criticism, and created a revised version of the argument in which the distinction between "because" in the sense of physical causality, and "because" in the sense of evidential support, became the central point of the argument.
More recent critics have argued that Lewis's argument at best refutes only strict forms of naturalism that seek to explain everything in terms ultimately reducible to physics or purely mechanistic causes. So-called "broad" naturalists that see consciousness as an "emergent" non-physical property of complex brains would agree with Lewis that different levels or types of causation exist in nature, and that rational inferences are not fully explainable by nonrational causes.
Other critics have objected that Lewis's argument from reason fails because the causal origins of beliefs are often irrelevant to whether those beliefs are rational, justified, warranted, etc. Anscombe, for example, argues that "if a man has reasons, and they are good reasons, and they are genuinely his reasons, for thinking something—then his thought is rational, whatever causal statements we make about him". On many widely accepted theories of knowledge and justification, questions of how beliefs were ultimately caused are viewed as irrelevant to whether those beliefs are rational or justified. Some defenders of Lewis claim that this objection misses the mark, because his argument is directed at what he calls the "veridicalness" of acts of reasoning, rather than with whether any inferred beliefs can be rational or justified in a materialistic world.