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The argument from reason is an argument against metaphysical naturalism and for the existence of God (or at least a supernatural being that is the source of human reason). 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'' (1960), Lewis substantially revised and expanded the argument. ==The argument== Metaphysical (or philosophical) naturalism is the view that nature is all that exists. Naturalists deny the existence of God, 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 (P therefore Q) 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 (or "valid", as Lewis sometimes says) 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 (animals exhibit patterns of behavior; these patterns are likely to be repeated; this dog has exhibited aggression towards someone who approached it; there is a good chance that the dog may exhibit the same behavior towards me if I approach it). 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 (natural selection), his argument does not follow from logical inference.
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 (such as neurochemical events in the brain) that are nonrational.
5. Therefore, there is not, and cannot be, good reason to accept naturalism.〔Adapted from Victor Reppert, author of "C.S. Lewis's Dangerous Idea. Taken from his blog at: http://dangerousidea.blogspot.com/2006/07/argument-from-reason-and-lewiss-post.html"〕 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 (God). This extension of the argument from reason states: 1. Since everything in nature can be wholly explained in terms of nonrational causes, human reason (more precisely, the power of drawing conclusions based solely on the rational cause of logical insight) 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 (from 2). 4. So human reason must come from a source outside nature that is itself rational (from 1 and 3). 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 (from 4-5). (Lewis, ''Miracles'', chap. 4) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Argument from reason」の詳細全文を読む スポンサード リンク
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