Analogy

In common use, accidental resemblances; in logic, often a form of inductive inference. It is better to say that induction is founded upon e ential, and analogy upon accidental qualities and resemblances. The former gives probability and the latter only rational po ibility. Parables are good illustrations; they are not arguments, but means of making a doctrine intelligible. As Jevons remarks, analogy "denotes not a resemblance between things, but between the relations of things. A pilot is a very different man from a prime minister, but he bears the same relation to a ship that the minister does to the state, so that we may analogically describe the prime minister as the pilot of the state. There is a real analogy between the tones of a monochord, the sages of Greece, and the gates of Thebes, but it does not extend beyond the fact that they were all seven in number." E.g. , the argument from the existence of terrestrial to that of planetary inhabitants has no cogency, and at best can only suggest a rational po ibility.