Full Idea
Always separate sharply the psychological from the logical, the subjective from the objective.
Gist of Idea
Keep the psychological and subjective separate from the logical and objective
Source
Gottlob Frege (Grundlagen der Arithmetik (Foundations) [1884], Intro p.x)
Book Reference
Frege,Gottlob: 'The Foundations of Arithmetic (Austin)', ed/tr. Austin,J.L. [Blackwell 1980], p.-3
A Reaction
This (with Ideas 7732 and 8415) is said to be the foundation of modern analytical philosophy. It contrasts with Husserl's 'Logical Investigations', which are the foundations of phenomenology. I think it is time someone challenged Frege here.
Related Ideas
Idea 7732 Never ask for the meaning of a word in isolation, but only in the context of a proposition [Frege]
Idea 8415 Never lose sight of the distinction between concept and object [Frege]