ABSTRACT
The conscious devisers of paradoxes can find little that is more amusing to them than the denial of the irreversibility of time; so strongly is it implicitly affirmed by common sense. Nevertheless, in spite of, or because of, the easy obviousness of the irreversibility of time in experience, its denial, at least as an interesting hypothesis, has had a certain attraction to many. Physicists themselves are not as a rule concerned to make definite pronouncements regarding the irreversibility of time. It is, first, necessary to distinguish between two different senses in which 'irreversibility' is used. First, there is 'irreversibility' proper, used only of an order which cannot be reversed. Secondly, the word is often also used for what would better be called 'unreversed', of an order which is not, in fact, reversed. The problem of irreversibility is in great part a pseudo one: and its genuine difficulties are great enough without adding to them.
