The Commens Dictionary
Quote from ‘Carnegie Institution Correspondence’
Deduction is divisible into sub-classes in various ways; of which the most important is into Corollarial and Theorematic. Corollarial deduction is where it is only necessary to imagine any case in which the premisses are true in order to perceive immediately that the conclusion holds in that case. All ordinary syllogisms and some deductions in the logic of relatives belong to this class. Theorematic deduction is deduction in which it is necessary to experiment in the imagination upon the image of the premiss in order from the result of such experiment to make corollarial deductions to the truth of the conclusion. The subdivisions of theorematic deduction are of very high theoretical importance.
‘Theorematic Reasoning’ (pub. 06.01.13-12:14). 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-5.