In the traditional interpretation mankind is a unity because it is, so to speak, a genealogical tree of which each man’s personal life is a branch. I suggest rather that the unity of mankind must be thought of as a unity in history, a unity in a play with one plot in which each man has a rôle. Just as Aquinas conceived of a biological intention of nature presupposed to all personal intentions, and of the propagation of mankind as presupposed to all personal lives (and therefore in a position to taint them); so we must conceive of an intention of history, which I call its plot, underlying every man’s personal life in so far as that life is a rôle in the total play. Just as a man, on Aquinas’ picture, is to some extent determined by an intention of nature even before he begins to take personal charge of his life, so too man’s life must receive sense from the part it plays in the whole play, even before one judges of the success or non-success of the way he personally played that part.

I would suggest, indeed, that this notion of a plot in history more truly expresses the nature of man than any genealogical or biological concept. For if, in some unimaginable future, intelligent animals were discovered on some other planet who belonged to some quite different branch of the biological tree, nevertheless, because they were intelligent animals, it would in principle be possible for us to communicate with them, for us to affect each other’s culture, and for us to grow into having one history with them.