Charles S. Peirce In the doctrines which have thus far been developed, are implicitly involved certain conceptions of such universal applicability and such importance in logic, that I propose to consider them especially in this chapter under the name of Categories.
Logic Chapter ---. The List of Categories
MS 207 (Robin 385): Writings 3, 61
Winter 1972-73
In the ideal final opinion which would perfectly represent the reality of things, all possible doubt would be resolved. It follows that the reality is something entirely definite. Ens est unum. An object may be conceived to have this character without being real, that is without being in accord with the opinion to which observations are fated to tend, and I shall call this the being of things. A griffin is a fabulous animal. That is, a griffin is supposed to be a definite object. You may ask as many questions as you please about a griffin and supply answers according to some rule and if all the questions which could be invented were thus answered, the animal would possess as perfect a being as if it were real, and yet be a mere creature of the
imagination.
In every doubt there is one thing fixed and one thing vague; the thing which we doubt something about is fixed, what we doubt about it is vague. These two things must equally be distinguished in the belief in which the doubt is resolved. Consequently, every being has elements which are distinguished from it but which belong to it, in short it has qualities.