A fond, foolish piece of vanity, the wish that one could somehow return to some previous point in time, that one could take an opportunity that had never existed. The Swiss postal clerk would have explained the impossibility of the wish; that linear time was a matter of convenience; that past, present and future occur simultaneously; that space-time is a continuum, so is complete in itself.

Logic rarely directs the business of the human mind. A notion persists that something was lost, that if only there had been a chance …