(1) I am intrinsically valuable and a bearer of rights by virtue of being me. So, for example, if you decide you want to kill and eat some living entity, and if that living entity turns out to be me, then you are poised to commit a very serious moral wrong. Regardless of my condition or circumstances, the fact that the entity in question is me is what matters morally. I matter simply for being who I am -- for being me.
(2) I was once an embryo and fetus, just as I was once a newborn, toddler and adolescent. This truth is confirmed by intuition and sound philosophical analysis informed by the scientific facts of human development. Therefore, to have killed the fetal human being in my mother's womb 26 years ago would have been to kill me. From these two claims, it follows that it would have been wrong to kill the unborn human being I once was. By extension, it is wrong to kill all unborn human beings, who are the same beings as their future adult selves, and who have a right to life simply by virtue of who and what they are.
A defender of the moral permissibility of abortion will probably have to deny either (1) or (2). Which one, and on what grounds? It is an unenviable task.
