An organism, a family, an organisation, a mind all of these are determined by the possession of an immune system. They need to identify what it not self and to find ways to exploit it and reject it, and they have no similar need to identify what is self. Defining the self, if it occurs, is only to serve as a further means of dealing with the not self, such means themselves forming a bewilderingly diverse array, with perhaps its own immune system. This is a somewhat positive spin on the Heraclitean insight of nature as pervasive war. As in history anything that emerges as a being has emerged out of war.