Readers of these essays will by now have formed the impression that I am committed to rescuing metaphysics from the jaws of physics. One manifestation of this mission is my opposition to reducing time to a quasi-spatial dimension and its further reduction to numbers. Thus reduced, time becomes a mere variable – t – that has no qualities, only numerical values, and none of the features that make it central to human life. For example, little t, unlike time as we experience it, has no tenses. The difference between, say, a regretted past and an anticipated future is lost.

I could go on about the poverty of t but I won't because I am also aware that in taking t for granted I am overlooking something rather extraordinary: the mysterious verb “to time”. While all beings (pebbles, trees, monkeys) are in some (very difficult to characterize) sense “in” time – immersed or dissolved in it – we humans are alone in timing what happens, including (or especially) what happens to ourselves and our very lives. We portion time into days and number days – and parts of them – and know that our days are numbered. Of all the occupants of the solar system – rocks, trees, lemurs and so on – we alone use the relative movements of its components to organize our own affairs.