Full Idea
An idea, insofar as it is an idea, involves an affirmation or negation.
Gist of Idea
An idea involves affirmation or negation
Source
Baruch de Spinoza (The Ethics [1675], II Pr 49 sII)
Book Reference
Spinoza,Benedict de: 'Ethics', ed/tr. Curley,Edwin [Penguin 1996], p.64
A Reaction
Spinoza clearly distinguishes ideas from images, and here seems to identify ideas with propositions. Nowadays we say these are 'true or false', but Spinoza is more personal and psychological. I prefer his way of putting it.
Related Idea
Idea 5776 A proposition is what we believe when we believe truly or falsely [Russell]