The Commens Dictionary
Quote from ‘Material Logic’
Formal logic classifies arguments by producing forms in which, the letters of the alphabet being replaced by any terms whatever, the result will be a valid, probable, or sophistic argument, as the case may be…
DPP 2:44; CP 2.549
‘Formal Logic’ (pub. 11.08.17-11:07). 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-material-logic-0.