A is A.

"Existence is the perceptually self-evident fact at the base of all other knowledge, i.e., that "existence exists."

To be is to be something, that "existence is identity." That is, to be is to be "an entity of a specific nature made of specific attributes." That which has no nature or attributes does not and cannot exist.

The axiom of existence is grasped in differentiating something from nothing, while the law of identity is grasped in differentiating one thing from another, i.e., one's first awareness of the law of non-contradiction, another crucial base for the rest of knowledge.

A leaf ... cannot be all red and green at the same time, it cannot freeze and burn at the same time... A is A."

—Ayn Rand