We do not generally afford the same rights to potential things that we afford to things. For instance, we do not give the child all of the rights an adult has. An adult has the right to vote, and though a child is a potential adult, we do not grant it the right to vote. The same can be said of other things. Since we do not tend to give the same rights to potential things, there is no reason a potential person should have the same right to life a person has.