The Commens Dictionary

Quote from ‘Letters to Paul Carus’


The names which I would propose for general adoption for the three different kinds of acceptability of propositions are


The last alone seems to be capable of a certain degree of exactitude or measurement

By plausibility, I mean the degree to which a theory ought to recommend itself to our belief independently of any kind of evidence other than our instinct urging us to regard it favorably. All the other races of animals certainly have such instincts; why refuse them to mankind? Have not all men some notions of right and wrong as well as purely theoretical instincts? For example, if any man finds that an object of no great size in his chamber behaves in any surprising manner, he wonders what makes it do so; and his instinct suggests that the cause, most plausibly, is also in his chamber or in the neighbourhood. It is true that the alchemists used to think it might be some configuration of the planets, but in my opinion this was due to a special derangement of natural instinct. Physicists certainly today continue largely to be influenced by such plausibilities in selecting which of several hypotheses they will first put to the test.

1910 [c.]
ILS 274-5; CP 8.222-223
‘Plausibility’ (pub. 19.09.14-16:14). Quote in M. Bergman & S. Paavola (Eds.), The Commens Dictionary: Peirce's Terms in His Own Words. New Edition. Retrieved from
Sep 19, 2014, 16:20 by Mats Bergman
Sep 19, 2014, 16:14
Last revised: 
Sep 19, 2014, 16:21 by Mats Bergman