Principles of Analogy

One clear strategy of argumentation when reasoning about things that are uncertain is to see whether they are similar to things that we do know and then draw conclusions about them on the basis of the similarities. Logicians call this strategy the ‘Argument from Analogy’. An analogy is a comparison of two things or analogues. For example, Julian Huxley offered the following comparison: “The relation between predator and prey in evolution is somewhat like that between methods of attack and defence in the evolution of war.” In comparing these two things, Huxley hopes to shed light on the first pair because of what we know about the second pair. But Huxley is not here providing an Argument from Analogy, and the first thing we should note is not to assume that the presence of an analogy in argumentation means the argument scheme is being used. Huxley provides no details of how the two pairs are alike; nor, crucially, does he draw a conclusion on the basis of the similarities. This latter feature is a key identifying feature of the Argument from Analogy.

The basic fallacy associated with the Argument from Analogy is called False Analogy. Understanding how the scheme works does not explain how false analogies can arise and what it is that is wrong with them, but it does help us appreciate how analogical reasoning differs from the other types of reasoning we have discussed.