Spencer Heath Archive

Item 425

Random taping by Spencer MacCallum from conversation at 11 Waverly Place, New York City, in which Heath answered a question how to distinguish and remember induction versus deduction

July 22, 1955

/From reading the college textbooks on inductive and deductive reasoning, you could easily get the idea that there are two systems of reasoning./ There are not two systems of reasoning any more than there are two systems of arithmetic. There are two systems of adopting premises from which to draw rational conclusions. One is to take premises from tradition, authority or unsupported imagination. Rational conclusions can be drawn from such premises, but such conclusions cannot be any more valid than were the premises from which they are drawn. The other system of choosing premises is to draw them from experience and observation, especially of facts and events that can be numerically described. Upon such factual premises, the same kind of reasoning is employed as was applied to premises drawn from tradition or authority. This process of reasoning is the same in both cases. It is called deduction. The only difference is in the source and kind of premises taken as foundation facts upon which to proceed.