What is "sentience"? Does it equal self-awareness?
[q]sen·tience (sĕn'shəns, -shē-əns)
n.
1. The quality or state of being sentient; consciousness.
2. Feeling as distinguished from perception or thought.[/q]
Ok, so "sentient":
[q]sen·tient (sĕn'shənt, -shē-ənt)
adj.
1. Having sense perception; conscious: “The living knew themselves just sentient puppets on God's stage” (T.E. Lawrence).
2. Experiencing sensation or feeling.
[/q]
Seems to me that by that definition, embryos/babies aren't "sentient" (self-aware) until around age, what, 3 months old? When do they normally start discovering their own hands and feet?
Or you could go the other way, and look at what stage the embryo begins "experiencing sensation or feeling." Definitely while still in the womb. How far along, though, I have no idea.
Personally speaking, I'm a pro-lifer, who firmly believes that bombing abortion clinics is unquestionably wrong. Personal beliefs is one thing, explaining your stance is fine as well. But forcing those beliefs on others - especially in a violent manner - is wrong.
EDIT: Oh, and I wonder what the stance of most PETA and SPCA people is on abortion.