An Introduction to Analogy
Analogy (derives from the Greek word ‘ἀναλογία,’(analogia), meaning “proportion”), is a comparison where one thing is compared with another on the basis of some similar features, typically for the purpose of explanation or clarification. For example, making a comparison between a computer and the human brain. Analogy also involves an inference where one thing is assumed to be similar to another in a specific respect based on the established similarity between the things in some other respect.
We often use analogy to draw a conclusion from the established facts between similarity of two things in certain respects to their similarity in some other respect. For insance: a breastfeeding-mother may reach a conclusion that breastfeeding will induce sleep to her baby because the baby soon fell asleep after she breastfed her the last time. Likewise, someone driving a Subaru STI Ltd may reason by analogy that a full tank will take him 270 to 285 miles given the fact that he had about 290 miles with the same capacity of fuel the previous time.
A general notion of this form of reasoning is that the things in comparison are alike in certain states, so they will almost always be alike in some other state. But reasoning with analogy doesn’t really bring justification as the factors that determine these things almost always varies in each respect.
In the sphere of logicOpens in new window, analogy is a form of induction that, on the basis of certain similarities observed between a known thing on the one hand and an unknown thing on the other, predicts the occurrence in the unknown of further similarities to the known. Chances are this kind of induction will almost always be sloppy in conclusion, as its end result produces propability rather than certainty.
Analogy often makes use of comparisonOpens in new window devices like metaphorOpens in new window and simileOpens in new window to compare two things, as it is evident in the analogy attributed to Samuel JohnsonOpens in new window: “Dictionaries are like watches; the worst is better than none, and the best cannot be expected to go quite true.”
Analogies allow rhetors to move beyond the limitations of language because their meaning is not literal but is informed by context.