Now that we've examined the effects of beauty, or aesthetic emotion, we'll try to find its cause. In other words, we'll try to deduce from the various qualities of aesthetic pleasure the qualities that its object – beauty – must have.

The first thing we know is that self-interest plays no role in aesthetic emotion. We can only be truly disinterested in an object if it has no concrete reality, for anything that really exists always has a certain utility – if only that of being agreeable. When we see such an object, it immediately inspires an ulterior motive – we want to keep it for ourselves. Yet beauty generates no such motive, so beauty can't be real. Indeed, it's nothing but a concept, an ideal formed by the mind.

We've also said that aesthetic emotion is pleasurable. Pleasure is produced by the effect, on our minds, of an object that conforms to its nature (pain results in the opposite case). The only thing we know is ourselves, and we judge all objects according to their relationships with us. So if aesthetic emotion is pleasurable, it must be that beauty conforms to our nature.

In beauty, therefore, there must be something of human nature. This is what Saint-Marc Girardin quite rightly acknowledged in his course on dramatic literature. What we look for in art is something of ourselves. A landscape isn't beautiful in itself.