finitely minute that each of them ends in beginning, at once is and is not. Time is itself an instance of this. The present time is, it is the limit between the past and future; but it has no calculable duration: in being it is not. Its coming is its going. It disappears in appearing. It for ever vanishes in a new present. All present time, then, has Being and not-Being. It is past in the very act of being present. Time seems to have supplied to Heraclitus (according to an expression of Sextus Empiricus) one of the best exemplifications that can be adduced of a process or a Becoming, that is, of a flux in which Being and not-Being are one. Time is perhaps the best symbol by which the conception of Becoming, as the unity of Being and not-Being, can be expressed. The present moment is, otherwise there would be no time at all; the present moment is not, otherwise there would be no past and no future, nothing but an everlasting now.
24. To get some further insight into this rather difficult speculation, and to test Being and not-Being as the necessary moments of one indivisible conception, the conception of change; let us try whether change can be explained when we regard these two not as essential moments of one indivisible conception, but each of them separate conceptions. Let us consider Being and not-Being as two separate conceptions, and let us try whether we can explain change on that supposition. Let us say, then, that a
