ABSTRACTSummed up in the coinage of the term ‘pre‐embryo’is the denial that human beings, as such, begin to exist from the moment of conception. This denial, which may be thought to have significant moral implications, rests on two kinds of reason. The first is that the pre‐embryo lacks the characteristics of a human being. The second is that the pre‐embryo lacks what it takes to be an individual human being. The first reason, I argue, embodies an untenable view of what it is to be human. The second reason exploits certain logical difficulties which arise over the possibility of twinning. I question the relevance of the appeal to such difficulties and conclude that there is no good reason for denying that a human being begins to exist from the moment of c