A  more indirect, but in my view,  more sure, route to the conclusion that the past is unreal  takes off  from  the notion of identity over time.  I  argue that it is impossible to believe  both that the past exists, and also, as we all ordinarily do, that things persist through change.  Consider a green leaf turning brown in autumn.   You will agree: it has to be the same leaf that was once green that is now brown. For if it were a different leaf – a brown one – it could not be said to have lost its greenness since it never was green. But the great 18th Century philosopher, Leibniz stipulates – surely incontrovertibly – that a thing cannot be the same as itself and yet have divergent properties from itself. So it seems it has to be the same leaf in order to lose its greenness, but being the same leaf means precisely retaining its greenness: a contradiction.  So what you may say: philosophers’ worry is not ours: obviously things persist within limits, depending on their kind. But, are you saying, we will reply, that it requires less than identity to persist?   These are deep and difficult questions. It seems clear however that identity is an atemporal relation that cannot accommodate the unidirectionality of time’s arrow. It is eventually concluded that the contradiction cannot be resolved so long as the leaf’s having been green has an equal reality with the leaf’s being brown, and that this provides grounds for demoting the past, and maintaining that only present things exist.