PhysicsAristotle

Aristotle's Physics is not what the modern word suggests. It is an investigation into nature (physis), meaning whatever has in itself a principle of motion and rest. The question is not how to predict particular events but what it means for anything to change at all.

Books I and II lay the groundwork. Change requires three principles: matter, form, and privation. Nature acts for the sake of something; Aristotle defends teleology against those who, like Empedocles, attribute natural outcomes to chance. The four causes (material, formal, efficient, final) are introduced here and applied relentlessly. To understand anything natural is to answer all four "why" questions about it.

Books III through VI tackle the concepts that make change intelligible: infinity, place, void, and time. Aristotle denies an actual infinite, admits only a potential one. Place is the innermost boundary of the containing body. The void does not exist; motion does not require empty space. Time is the number of motion with respect to before and after.

Books VII and VIII argue for an unmoved mover. Every chain of movers requires a first member that moves others without itself being moved. This argument connects the Physics to the Metaphysics and, through Aquinas, to the whole tradition of natural theology.

The Physics governed the scientific imagination for nearly two thousand years. Newton's mechanics displaced its specific claims, but every subsequent debate about causation, space, time, and infinity still works within or against categories Aristotle defined here.