Focussing the Debate: When does a Human Being Begin Existing?

I want to focus this debate. It gets too sprawling, as you know.

Pro-choice thinks abortion is permissible
Pro-life thinks abortion is murder

let's leave aside the nuances, for a minute.

The reason why pro-lifers think abortion is murder is that they think abortion ends the life of a human being, which is an injustice against that defenseless human being.

Pro-choicers think abortion is okay for different reasons, but are agreed that the pro-lifer is wrong to think abortion is wrong; pro-choicers (I assume) agree that ending the life of another defenseless human being is an injustice.

So, when does a human being begin existing?

Pro-lifers seem to be able to point to a very clear an definite beginning point for a human being, namely, conception-fertilization.

Pro-choicers have vainly sought to specify some other point after conception, such as when there is sentience, brainwaves, heartbeat, viability, etc. But all these fail to distinguish *being human* with *functioning as a human*. In the end, then, such attempts are *arbitrary* definitions of when human beings begin. All the while, the pro-lifer is saying, "But conception-fertilization isn't arbitrary and it makes good sense"

So,

Pro-choicers fall back on the agnostic position, or the gradualist view. Who know's when a human being begins? At some point it does. Well, let's name that point. Say, 8 months into the pregnancy. What about 7.5 months? 7 months? As we go back in time, on the gradualist view it is less and less probable that we are looking as a human being. But how much less? And all the while, the pro-lifer is saying, "But conception-fertilization isn't arbitrary and it makes good sense."

The Upshot


Pro-life philosophy has a clear answer to when a human being begins existing.
Pro-choice philosophy does not have an adequate answer.

Pro-life philosophy, because of the clear answer, can move to the ethical questions with greater clarity, and then to the political scene with a definite and well-grounded principle.

Pro-choice philosophy, in not having an adequate answer to when human being begin existing, flounders on the ethical questions, and goes into the political scene with an assortment of concerns, even real injustices to be dealt with, but lacks clear and definite, well-grounded principles that, in turn allow us to address all or at least the biggest injustices our society faces.