Abstract

Let S be the set of all entities that exist (or have existed). Define the relation <= on S by saying that x<=y if and only y is a cause of x. By verbal fiat we will define x to be a cause of x for all x in S (if we do not accept this definition, our assumptions will be slightly different; however, it is clear that the existence of x is necessary and sufficient for the existence of x, and that the existence of x is never strictly temporally posterior to that of x, so calling x a cause of itself is not such a bad idea.) Then, <= is transitive, and moreover if x<=y and y<=x, then x=y (i.e., there are no circles of causation). Hence, <= defines a partial ordering on S.