The case for abortion that depends on denying any right to life to the human embryo, according to a limiting standard of what constitutes “true” human life, was always on shaky ground. Modern medical experience and practice seem to have nullified that limiting standard outright from an empirical point of view. Common sense, which is to say basic human logic, has always nullified it from a biological point of view. As long as we choose to remain a civilization even rhetorically wedded to the idea of rights grounded in certain truths about human nature, there really is no legitimate case to make for ending a vulnerable life merely because one regards its presence as inconvenient, anymore than I can, in a rights-based society, make a case for property theft on the grounds that someone else’s possession of things I desire is frustrating to me.
There may be another kind of case to make for abortion, based on very different social principles and standards of political right and wrong. But to make it, one would first have to jettison all deference to the concept of rights, i.e., to the standard of individual freedom and natural equality, outright. Hence, the modern case for abortion, prioritizing a pregnant woman’s “right to choose” where her own body is concerned, is, shall we say, stillborn. The self-ownership assumption of this argument is a property rights assumption, which means its force depends entirely on deference to the idea that all human individuals have rights which must be protected. And this assumption, once adopted, intrinsically contradicts the claim of a right to abortion, since in a society based on equal rights, the self-ownership rights of one human being can never be allowed to supersede the self-ownership rights of another.
I cannot justify my wish to kill an innocent human being by claiming that as a self-owning individual, I have a right to choose how to use my body, and in this case I choose to use my body to beat a man to death with a club (or, if you prefer, to stab him in the head with scissors). For this means explicitly denying and violating that innocent man’s self-ownership rights, thereby implicitly denying my own.
If you wish to return to a pre-natural-rights political orientation, and make your case for abortion on the basis of theoretical calculations of civic well-being, for example, or on judgments of the proper population number, or on a community preference for eliminating the unhealthy, or what have you, feel free to make that case. But remember that you cannot have your cake and eat it too. You cannot regard yourself — or expect anyone else to regard you — as a rights-bearing individual, once you have chosen to dispense with the notion of a civil society grounded in human rights, which you do the moment you argue that your personal interests take priority over another person’s ability to simply live.
In short, if a developing human embryo, on your view, has no enforceable rights to life or self-determination, then neither do you, so you may not use your alleged rights as grounds for any choice. If, on the other hand, you wish to continue employing the concept of rights, and specifically employing it as grounds for determining what you must be permitted to do with your own life and body, then you must accord the same rights and grounds to every other human being who has not directly forfeited that accordance in some manner.