This from a reader:
I enjoy reading Maverick Philosopher even though I seldom agree with the conservative viewpoint. The thing that I find most interesting about your articles on abortion is that they really do not address what I consider to be the central issue and that is when does human life begin. Zygote, blastomere, embryo, fetus? I would be interested in your ideas.
Well, I did address this question on the old blog. But in philosophy one is never done revising and re-thinking, so let me take another stab at this.
1. Note first that your question -- When does human life begin? -- is not exact. Presumably, what you are asking is: When does a human life begin? Our concern is with the origin of particular human lives, not human life in general. Even so, the question remains unclear. Here are two possible disambiguations of 'When does a human life begin?' given that the context is the morality of abortion:
Q1. When does a life become human in a sense of 'human' that justifies ascription of the right to life?
Q2. When does a life become human in the biological sense of 'human'?
The questions are distinct; the first is normative, the second non-normative. A defensible answer to Q2 is 'at conception.' If the gametes come from human parents, then the zygote that results from the joining of sperm and egg must be biologically human -- it cannot be biologically lupine or bovine, say -- and it will typically be biologically alive (as opposed to dead or inanimate: neither alive nor dead). So there is biologically human life right from conception. This is undeniable.
But someone who gives, and must give if he is reasonable, this answer to Q2 may go on to deny that the zygote has a right to life, and do so reasonably. It might be said that the zygote lacks a right to life because it lacks those capacities (self-awareness, etc.) possession of which is necessary for an entity to be a right-possessor. I don't accept this view, but it is a 'reasonable' thing to say. (The reasonable is not the same as the true.) I don't accept it because of my earlier potentiality argument. But one could also take the view, regardless of considerations of potentiality, that all instances of innocent biologically human life fall under the general prohibition against homicide, regardless of how young the human life is.
2. Without getting into the specifics of these arguments, my present point is that Q1 and Q2 must not be conflated: they are distinct questions. Q2, however, is itself ambiguous as between Q2 and the following specification of Q2:
Q2-S. When does a life become a biologically human individual?
Every biologically human individual is a biologically human life, but we cannot assume that every biologically human life is the life of a biological individual. A zygote that arises from human gametes is of course human and alive. So it is a human life in one sense of that phrase. But is it a biological individual? That depends on what we mean by 'biological individual.' Let this be our working definition:
D1. X is a biological individual =df X is a single living thing that is not a mere aggregate of smaller living things, nor a mere part of a single living thing, but has a life of its own which it seeks to preserve and develop.
No one, for example, will say that three cats form a biological individual. A set, mereological sum, or concrete aggregate (three cats held in my hands, say) is not itself a living thing with a life of its own. Nor is the blood of a cat a biological individual. But I am a biological individual, and so are neonates and late-term fetuses. Why not same the same of human zygotes? Here is an argument for consideration:
(P1) Every innocent biologically human individual is subsumable under the general prohibition against homicide; (P2) The zygote is an innocent biologically human individual; therefore, (C) the zygote is subsumable under the prohibition, which is to say that to kill it is morally wrong, except perhaps in certain unusual circumstances.
The 'speciesism' objection has been brought against P1 and the 'twinning' objection against P2. I plan to discuss these objections in later posts.
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