I've see no secular reason why very early term abortions should be prohibited. To explore this further, I went to Google+ and spoke with Catholic Apologist, Paul Schlenker.
Me: What's the harm in painlessly killing something that is not only unaware and unconscious; but incapable of pain, awareness and consciousness if not for some assumption of a soul?
Paul: The harm is that by killing an embryo that is unaware, unconscious, and incapable of experiencing pain is that you prevent that innocent human being from developing further, being born, and living the life it has a right as a human being to live.
Me: So, outside of preserving the embryo's potential, the only negative affect is the emotional reaction you and others who are uncomfortable with abortion experience, right? The potential argument is problematic now that any instance of DNA can be said to have the same potential when you consider cloning, not to mention the potential of a sperm and egg. To say everything with human potential must be realized in our modern world would result in overpopulation and the waste of human hair and tissue a felony. (Yes, this highlights advancements of science into an argument about otherwise natural development, but without taking into account modern science we couldn't know a women is pregnant early enough for this debate to be relevant.)
Paul: Human hair and human tissue are human life, but they aren't human beings. A fetus is a human being. Human hair and human tissue are part of a human being, but they aren't, in and of themselves, human beings.
Many pro-choice people say that abortion is justified because a fetus is only a "potential life", not an actual life. I think that's rubbish. A fetus is an actual human being from the moment of fertilization, and it is fully alive. If a fetus is only a "potential life", at what point does it become an actual life? The only logical and reasonable point at which a fetus becomes an actual life is at the moment of fertilization.
Me: The point was obviously missed in regards to hair and tissue. You must acknowledge that no harm is done from the point of view of the embryo, because the embryo has no point of view. If not for potential, I don't understand your argument that there is harm done.
Paul: Do you think it should be permissible to kill a person in a coma?
Me: No, I don't think it should be permissible to kill a person in a coma if they are likely to come out of it. If they certainly won't, then it is fine. The difference is that an agreement to kill coma victims sets a precedent that could directly affect me, people I care about, or people others care about. I don't want them killed if and when they are in a recoverable coma, therefore I don't want any coma victims killed. Do unto others, as they say. Also, even though neither the coma victim nor the embryo want to die--(because they can't want anything) family members and friends almost certainly want the coma victim to reach the potential of regained consciousness while the parents of the embryo obviously don't want the embryo to reach consciousness because otherwise the question of abortion would be moot.
I edited this conversation to make it easier to read and filter out the peanut gallery. The entire thread can be read here. Abortion is one of the few topics involving religion in which I haven't completely made up my mind. Maybe your input will help me with that.