What is the relation between time and change? Does time depend on the mind? Is the present always the same or is it always different? Aristotle tackles these questions in the Physics. In the first book in English exclusively devoted to this discussion, Ursula Coope argues that Aristotle sees time as a universal order within which all changes are related to each other. This interpretation enables her to explain two striking Aristotelian claims: that the now is like a moving thing, and that time depends for its existence on the mind.