The Commens Dictionary

Quote from ‘Cambridge Lectures on Reasoning and the Logic of Things: Types of Reasoning’


We see three types of reasoning. The first figure empraces all Deduction whether necessary of probable. [—] The third figure is Induction by means of which we ascertain how often in the ordinary course of experience one phenomenon will be accompanied by another. No definite probability attaches to the Inductive conclusion, such as belongs to the Deductive conclusion; but we can calculate how often inductions of given structure will attain a given degree of precision. The second figure of reasoning is Retroduction. Here, not only is there no definite probability to the conclusion, but no definite probability attaches even to the mode of inference. We can only say that the Economy of Research prescribes that we should at a given stage of our inquiry try a given hypothesis, and we are to hold to it provisionally as long as the facts will permit. There is no probability about it. It is a mere suggestion which we tentatively adopt.

RLT 141-142
‘Retroduction’ (pub. 12.03.13-18:45). Quote in M. Bergman & S. Paavola (Eds.), The Commens Dictionary: Peirce's Terms in His Own Words. New Edition. Retrieved from
Mar 12, 2013, 18:45 by Sami Paavola
Last revised: 
Jan 07, 2014, 00:58 by Commens Admin