The common methods of thinking are deduction and induction. The former method tries to establish a specific and limited conclusion by showing that it is allied with, or conforms to, a general truth or principle. In deduction, thought moves from the general to the particular: "From the general principle (fact) that most Scandinavians have blue eyes, the deduction may be made that Lars, a Scandinavian, probably has blue eyes." Induction seeks to establish a general truth, a principle. In induction, one observes a number of facts, classifies them, and arrives at a conclusion, or principle: "From observation of hundreds of Scandinavians, most of whom have blue eyes, one may induce (make an induction) that most Danes have blue eyes," Through induction, the laws (principles) of science have been arrived at. Through deduction, these principles (laws) are applied in specific situations, such as the development of a vaccine or the manufacture of a synthetic fiber.
Dictionary of problem words and expressions. Harry Shaw. 1975.