What have we to appeal to in order to reinforce the notion that the right to life once conceived is an inalienable right? Don't we first have to establish from whence comes the inalienable? Could we do that by the following?...
That the human race exists is 'self-evident'. That we appear to be the only species on earth with the reflective quality of valuing other living beings not directly connected to our continued existence is only slightly questionable (elephants appear to have some 'mourning' instinct over lost fellow elephants; my present cat companion appeared to 'miss' our other cat friend when he was run over in the street). In the absence of any evidence that any other species has made any form of acknowledgement of a Creator, that trait also seems uniquely human. Is there an a priori value to individual human life? Only if we acknowledge such. What if we don't acknowledge that, as with Singer? Have we, in denying an a priori value to individual existence, negated the ONLY reason for our own individual existence?
Put another way: If we acknowledge that we are a created creature--by a Creator or by evolutionary chance, somehow existing at a higher than any other species level, don't we cancel our own individual right to existence when we deny the value of ANY OTHER individual human's existence, whether in embryonic age or after decades of existence?