Catholic Dictionary




Originally meant the appearance or visible form of a thing existing apart from the thing itself. Consequently, the likeness within the mind of some reality that exists outside the mind. An idea is clear when it is distinct from other ideas; it is complete when it adequately represents the nature of what is mentally conceived; it is primitive when acquired directly from the object known; and derived when arrived at from other ideas by comparison and contrast. (Etym. Greek idein, to see.)