Motion & Change

Kinēsis (κίνησις) means motion or change — not only movement through space but every kind of becoming: growth and decay, alteration, coming-to-be and passing-away. It is the root of our 'kinetic' and 'cinema', and the central problem of Greek natural philosophy.

The challenge of Parmenides

Parmenides had argued that change is impossible, even unthinkable: for a thing to change, what-is would have to come from what-is-not, and non-being cannot be. His denial forced every later thinker to explain how change is so much as possible — how to save the appearances of a world plainly in flux.

Aristotle's solution

Aristotle answered with the pair potentiality and actuality: change is the actualizing of a potential, the passage of what is potentially hot into being actually hot. Defined precisely, kinēsis is 'the actuality of what exists potentially, insofar as it is potential'. By this analysis he reconciled the reality of change with the demand for intelligibility, and made a science of nature (physis) possible. For Plato, by contrast, the moving world of the senses was the realm of opinion, set against the changeless Forms that alone can be known.