Life begins at conception, but personhood does not. Consider this argument, which I posted to dad above:
1. What is a human person? Anything possessing human DNA? Obviously not. A scrap of skin, an appendix, an arm or leg - these things are not people.
2. Well then, a living human body? That sounds closer. But consider this: imagine a "brain dead" human body in which the brain is completely, medically dead, totally incapable of recovery, but the body can be sustained - and could, in theory, live indefinitely. Would you say this body, without a brain, was a person? I think we would all agree that it is not.
3. Therefore, we arrive at the conclusion that "personhood" resides in the possession of a working brain (if you disagree with this, please explain why). To forestall some objections I have heard to this, people who are asleep, stupid, mentally disabled or suffering from dementia still possess the ability to think, and so qualify as persons.
4. A baby does qualify as a person before it is born, as the brain is developed and active. However, that is no problem, as abortions are not performed during this time. All abortions (with exceptions for emergencies, such as when the baby is crippled to such a point that life would be a living hell for them) take place long before the baby's brain has begun to work, or is even present.
6. Therefore, abortions are not murder. They are the aborting (stopping development) of a potential human person, yes, but not yet a person.