By the Parmenidean dogma I mean the proposition that “something cannot come put of nothing.” If you like to add the other half of the common statement it is that “something cannot become nothing.” But in this paper I shall be thinking mainly of the first proposition. I call it the Parmenidean dogma because, although it may have been implicit in much human thought before Parmenides, it was he, so far as I know, who first made it explicit in the form of an abstract metaphysical proposition.