Idea. What is an idea? We say there are ideas of triangle, of animal, of God. How are these under the same denomination of ideas?

Perhaps we must say: an idea is a thing. But then we enter the system of Protagoras, which Plato already so well criticized.

If an idea equals a thing, since one man has an idea of God and another man an idea of no‑God, to each of these ideas corresponds a thing.

Now, since the ideas are opposite, so are the things and this is impossible. (Answer to this: there is no idea of no-God.) There is no idea of nothing. An idea of nothing is no idea.

But, then, there are, for one man an idea of God, for another man an idea of Fate and for another an idea of Matter. Each of these is an idea, all of these ideas have the same degree of clearness — they nevertheless contradict each other.

Characteristics of an idea, e.g. the idea of circle. Unity. Perfection. Simplicity.

Idea = possibility.

Idea of form.

Idea of triangle.

Idea of scalene triangle.

Idea of a particular scalene triangle which I have just drawn.