Full Idea
Consider what effects, which might conceivably have practical bearings, we conceive the objects of our conceptions to have. Then, our conception of these effects is the whole of our conception of the object.
Gist of Idea
Our whole conception of an object is its possible practical consequences
Source
Charles Sanders Peirce (How to Make our Ideas Clear [1878], EP i.132), quoted by Albert Atkin - Peirce 2 'early'
Book Reference
Atkin,Albert: 'Peirce' [Routledge 2016], p.31
A Reaction
This is his 1878 version, which was fine-tuned later in life. He seems to have extended his principle to include possibilities, as well as the mere objects. That is, he moved beyond mere nominalism.