Singer voices here perhaps the most popular argument in favor of embryo-destructive research and abortion. Few who accept this argument have followed it to its logical conclusion, however, as Singer has: If self-awareness is the ground of general immunity of being killed right not to be killed, not only abortion but also infanticide, and the killing of many helpless adults, are morally legitimate. In fact that conclusion is inescapable once one accepts Singer's premise. But one has decisive reasons to reject that premise as fatally flawed.
It is true that an embryo or fetus (or infant) lacks the immediately exercisable capacity for self-awareness, rationality, or free choice. Yet, the embryo or fetus does have the basic, natural capacity for such actions as consequent to its nature, that is, as entailed by the kind of entity it is. The embryo or fetus, precisely in virtue of the kind of entity he or she is, has the capacity to develop himself or herself to the point where he will perform such actions. And no one has been able to give an intelligible reason why we should base full moral rights on immediately exercisable capacities—which can come and go—rather than on the basic, natural capacities that a human being at any stage of development has in virtue of the kind of entity it is.