The principle of moderation was termed the Golden ______ by Aristotle.

Golden Mean

In philosophy, particularly Aristotelian ethics, the desirable middle between two extremes, one of excess and the other of deficiency.

Principle

A fundamental truth or proposition that serves as the foundation for a system of belief or behavior or for a chain of reasoning.

Moderation

The quality of being moderate and avoiding extremes in behavior or expression, advocating for balance and restraint.