 It is natural to use the expression ‘the essence of …’, which implies sufficiency as well as necessity: possession of the essence of K suffices for membership of K, as well as being necessary for it. According to the foregoing, not all the arguments of Kripke and Putnam establish what the essence of some kind is, rather they establish only what we may call a partial essence, conditions that are necessary but not sufficient. This is clear in some other of Kripke’s arguments. Thus it is only a partial essence that someone originates with the gamete (sperm and egg) from which they in fact originate, since they might have a monozygotic (identical) twin who has the same origin. A further question is whether there is a full essence (the essence) for everything that has a partial essence.