PHIL1002 Lecture Notes - Lecture 3: Modus Tollens, Inductive Reasoning, Modus Ponens
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Analogy: there are two main types of inductive reasoning: analogies and generalisation, however the longer the list of shared properties the better the reasoning when using an analogy, the analogy of a painting: Descartes uses the analogy of how dreams resemble or draw from aspects of reality: the nature analogy: A watch has a purpose, structure and design. Nature also has a purpose, structure and design and therefore nature must also have a maker [god]. Et(cid:272): a=b, modus ponens [mode of affirmation]: If the antecedent [a] is true, then so must b [the consequent] A is true: therefore b is true, modus tollens [mode of denial] Therefore, a cannot be true either: the conditional is about logical relationships not merely casual relationships, consider the relationship between oxygen and photosynthesis on a planet being tested for life. It is necessary that o to say p [for photosynthesis to occur, it is necessary for oxygen to exist]
