The Commens Dictionary
Quote from ‘Carnegie Institution Correspondence’
My first real discovery about mathematical procedure was that there are two kinds of necessary reasoning, which I call the Corollarial and the Theorematic, because the corollaries affixed to the propositions of Euclid are usually arguments of one kind, while the more important theorems are of the other.
‘Corollarial Reasoning’ (pub. 06.01.13-12:06). 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-carnegie-institution-correspondence-3.