Infinity in Physics is treated as something that exists only potentially, rather than actually. Aristotle argues that magnitudes such as lines or time can be divided indefinitely, but this does not mean that an infinite quantity exists as a completed whole. This distinction allows Aristotle to respond to paradoxes about motion, such as those attributed to Zeno.

Matter is the underlying substrate that persists through change. In Aristotle’s work, matter does not exist independently as a fully defined thing. Instead, it exists as the potential that receives form. In Physics, matter explains how a substance can change while maintaining continuity, since the same underlying material can take on different forms.

Nature is defined by Aristotle as an internal principle of motion and rest present within natural things. Objects such as plants, animals, or the elements move and develop according to their own nature, rather than through purely external forces. The study of nature therefore focuses on understanding the causes and processes by which natural things change.

In Aristotle’s work, physics refers to the philosophical investigation of nature and natural processes. The subject concerns things that possess within themselves a principle of motion and change. Physics establishes the fundamental concepts—such as motion, causation, time, and infinity— that guide Aristotle’s broader study of the natural world.

A principle is a starting point or fundamental basis from which explanation proceeds. In Physics, Aristotle seeks to identify the principles underlying natural change, particularly matter, form, and privation. These principles provide the framework for understanding how and why natural processes occur.

Privation refers to the absence of a form that something has the potential to possess. In Aristotle’s explanation of change, privation represents the state from which a thing begins its transformation. For example, when something becomes hot, it moves from the privation of heat to the possession of heat.

The term qua, meaning “insofar as” or “in the respect that,” is used by Aristotle to clarify how something is being considered in an argument. In Physics, it often appears when discussing change, as Aristotle describes motion as the actuality of something that exists potentially qua potential. This distinction helps specify the precise aspect of a thing under discussion.

To argue sophistically means to reason in a way that is misleading or based on verbal tricks, rather than genuine logical clarity. In Physics, Aristotle occasionally accuses earlier philosophers or critics of arguing sophistically when they rely on ambiguous terms or deceptive reasoning. Identifying such arguments allows Aristotle to clarify his philosophical treatment of motion and change.

The phrase tout court means “without qualification” or “in the strict sense.” Aristotle uses this distinction to differentiate between something being described absolutely and something being described in a limited or qualified way. For example, something may be said to change tout court when referring to change of place, whereas other alterations may be called changes only in a qualified sense.