abstract

Two kinds of logical reasoning can be distinguished in addition to formal deduction: induction and abduction. Given a precondition, a conclusion and a rule that implies the conclusion given the precondition, we can differentiate the three kinds of logical reasoning developed by the philosopher C.S. Peirce.

*Deductive reasoning* determines whether the truth of a conclusion can be determined for that rule, based solely on the truth of the premises. Mathematical logic and philosophical logic are examples of this type of reasoning.*Inductive reasoning* attempts to support a determination of the rule. It hypothesizes a rule after numerous examples are taken to be a conclu- sion that follows from a precondition in terms of such a rule.*Abductive reasoning/ given a true conclusion and a rule, it attempts to select some possible premises that, if true, can support the conclusion. This kind of reasoning can be used to develop a hypothesis, which in turn can be tested by additional reasoning or data. Detectives and diagnosticians often use this type of reasoning.*

It is important to notice that inductive and abductive reasoning are not sound, in other words, they do not contain in themselves their logical validity and must be confirmed empirically: confirmation can never be absolute, but only in terms of probability.

outcomes