Hegel's Science of Logic is divided into three books: the doctrine of being, the doctrine of essence, and the doctrine of the concept. Being is the most immediate category; it proves to be empty and to pass into nothing; being and nothing unite in becoming. From there we move through determinate being, quantity, and measure.

Essence is the sphere of reflection: identity, difference, contradiction, ground. Essence is being that has come to mediate itself. The concept is the third book—subjectivity, objectivity, and the idea. Here thought is no longer external to its content; the concept is the self-determining universal.

The Logic is not a handbook of formal rules but the exposition of the categories through which thought must move to think reality. Each category is shown to be incomplete and to lead necessarily to the next. The system is the circle that returns into itself.