We argue that separation-survivability is a significant developmental fetal milestone beyond which abortion is only rarely and exceptionally morally justifiable. Secondly, we argue that the continuous nature of prenatal development, and simultaneous parallel development and actuation of intrinsic and contingent potentiality that eventually results in the development of a person capable of moral thoughts and deeds, implies continuously incremental moral significance. We propose that the moral justifiability of each instance of non-therapeutic pre-viable termination Should be the product of all internal dialectic or "moral enquiry". Arguments should be of increasing power in order to trump the sliding-scale increase in prenatal moral significance. We agree that sentience is morally significant, but argue that survivability is of predominant importance. since human beings who have the potentiality of separate, relatively independent lives, should, normally, be allowed to continue living. We argue for a moderate position on abortion.