 According to Grosseteste, the notion of eternity is key also to understanding the nature of time. In his commentary on the Physics he takes Aristotle’s conception of time as a number of change in respect of before and after to be the result of a superficial discussion, adequate as far as the natural philosopher is concerned but inadequate as an account of time’s true essence, an inadequacy, he thinks, Augustine had also seen. But Grosseteste is not attracted to what he takes to be Augustine’s subjectivist conception of time and instead seeks an account of the true essence of time as an objective phenomenon.