The Commens Dictionary
Quote from ‘Logic. The Theory of Reasoning. Part I. Exact Logic. Introduction. What is Logic’
Logic proper is the theory of reasoning. That is to say, it is the study which aims to ascertain what must be the perceptible relations between possible facts in order that the knowledge that certain ones are true may warrant us in assuming that certain others are not true.
This definition is opposed to the treatment of logic as a branch of psychology or as founded upon psychology. For according to our definition, it makes no difference to the logician whether a fact is thought in this way or in that way unless the distinction will alter our right to draw a conclusion.
‘Logic’ (pub. 28.02.18-11:50). Quote in M. Bergman & S. Paavola (Eds.), The Commens Dictionary: Peirce's Terms in His Own Words. New Edition. Retrieved from http://www.commens.org/dictionary/entry/quote-logic-theory-reasoning-part-i-exact-logic-introduction-what-logic-1.