The Commens Dictionary

Quote from ‘Logic. The Theory of Reasoning. Part I. Exact Logic. Introduction. What is Logic’


…it may perhaps be true that reasoning can only be performed by a mind more or less like that of man, although there are machines which will produce the conclusions from certain premises. But reasonings can be expressed in words, in algebraic formulae, and in diagrams; and such expressions have the same logical characteristics that the mental representations have. Logic, therefore, concerns itself as directly with the outward, as with the inward representations. On the other hand, among the characters of reasoning which are pertinent to logic, one of the chief is that reasoning is essentially of the nature of a representation or sign. In saying this, I anticipate one of the results of the study of logic, and the reasons which lead to this conclusion cannot be fully appreciated in advance of such study. The premise of a reasoning is supposed to be true, and as such it represents the real world, although only in part. The conclusion represents the very same world. Neither is the world; for one is no more so than the other; and were both the same world they would be identical. They are alike representations, or signs, of the world. But the reasoning does not lie in the premise nor in the conclusion nor in their mere aggregations. It lies in the representation that in every world an analogous conclusion would, either invariably or mostly, be true for every similar premiss that was true. Reasoning is therefore not only a representation, but a representation of possibilities.

Now what are possibilities, what mode of being have they but the mode of being of representations? Whether or not they have any real mode of being, I do not ask; for it is not here a pertinent question. I only say that so far as they are real, the real is of the nature of a representation.

1897 [c.]
PSR 41
‘Reasoning’ (pub. 28.02.18-11:47). Quote in M. Bergman & S. Paavola (Eds.), The Commens Dictionary: Peirce's Terms in His Own Words. New Edition. Retrieved from
Feb 28, 2018, 11:47 by Mats Bergman