Maximizing Moral Virtue

[Belacqua]

It isn't fair to say that all anti-abortion people rely on 1) cuteness, or 2) emotional dispositions toward similarity. To assume that they do would be to ignore, for example, the arguments from potency and act. Since such arguments are ancient and are assumed by many people to be rational, anyone who claims to be able to state anti-abortion reasoning in fair terms would need to be aware of this.

I may need to look up "act and potency," so let me know if I'm getting it wrong.  But whatever it is, I'd like to see how this argument is applied differentially to non-human developing mammals in utero, let alone to post-birth offspring.

If you're not vegetarian, then you must either believe or feel human exceptionalism, since you presumably would not tolerate the killing of humans for consumption, or the imposition of suffering in/by an industry with that purpose.  

I propose the following reasons for the sense of human exceptionalism, and ask you to provide any that might be missing.
-egocentric bias (anything like me is more important than things unlike me)
-religious proclamations ("God created man in His image.")
-protective instinct ("Squeeee!  It's cute, will die if necessary to defend it.")
-valuations of mental superiority: intellect and so on, along with the position that superior intellect makes something intrinsically more valuable.

I'd say egocentric bias in a non sequitur-- things are not intrinsically more value because they are like me.
Religious proclamation is irrelevant to a debate with someone outside your religion.  Why should I care what you claim your God says?
Protective instinct is based on the previously-mentioned fallacy-- specifically, the use of "baby" terminology for something that isn't a baby.
Valuations of mental superiority cannot matter when a fetus has no mind at all-- certainly not more than any mammalian fetus.

What, exactly, is being lost in an abortion?  There are many "human" things that do not need to preserved: corpses, clumps of hair, excrement.  That they are "human" isn't itself enough to merit protection or concern.

The act/potency argument is simply that an organism develops (actualizes) its potentiality throughout its life. 

The ontological change occurs at conception, because that is when the actualization of human potential begins. Neither the sperm nor the egg has the potential to develop into a full human, but the fertilized egg does. From there it's just a long series of changes, including the gradual development of cognitive capacity. This argument doesn't recognize an ontological change based on location (inside the mother or outside). Nor does it see a clear milestone at some point when the thingy develops a particular capacity -- say, for suffering or for reciting the alphabet or for taking moral responsibility for one's own actions. An individual develops many capacities continually, and is always at some stage in which some potentials are not yet developed. (Until one dies, at which time activation of potential ends. So that's another ontological change.) 

Nor does the argument recognize the dependence of the thingy on the mother (i.e. viability). Since after all no human being survives entirely through its own efforts, and a newborn baby is scarcely less dependent on its supporting adults than a fetus. 

The argument is Aristotelian, and you know of course that he was not a Christian and didn't argue for supernatural insertion of a soul. It was taken into Christianity by Thomas Aquinas. Of course he believed in a soul and in people being special to God, but the argument as stated doesn't rely on this -- it's natural theology, not revealed. 

As to whether humans are more special than animals, that is a separate question. The activation of potential works the same in any animal which develops from the contribution of two parents. If we take it as a given that humans are worth protecting, then the act/potency argument is relevant to the point at which they become worth protecting. 

Personally I am open to the argument that all animals are more valuable than we usually think of them. The monks at the temple near my house won't even swat a mosquito. (And there are 6-inch poisonous centipedes in this area who seem to need killing, if anything does.) The fact that I am not devoted enough to the issue to give up my cheeseburgers speaks to my own lack of commitment, and doesn't really affect the becoming-human argument.