Bibliography

On the Three Kinds of Reasoning [R]

By deduction I mean that kind of reasoning which if it be sound, and if its premisses are true, renders its conclusion certain.

…by Induction, or Inductive Reasoning, I mean all reasoning which infers that something is true of the whole of a given collection (no matter what kind of a collection it may be) because it has been found that the same thing is true of a part of that collection. [—] Pure inductive reasoning hardly ever, if indeed it ever does draw an altogether new and unanticipated conclusion. Its usual and proper business is to decide between inconsistent theories which we have been led to entertain by Retroductive Reasoning in order to account for different surprising phenomena. For we shall find that Induction is as far as Deduction from introducing into its conclusion any concept not already contained in its premisses. The true function of Induction is critical.

That kind of reasoning by which we are more or less inclined to believe in a theory because it explains facts that without the theory would be very surprising is what I call Retroduction, or reasoning from consequent to antecedent. To understand the legitimacy of this kind of reasoning (often and often as it deceives us,) is to understand the legitimacy, the truth-leading power of all reasoning.