Can Science Tell Us Anything?
There is no scientific basis for the existence of a soul, but there is no scientific basis for the existence of subjectivity, either, which makes it difficult to ascertain concepts such as "sanctity." Physics alone can't tell us whether a human life is worth more or less than a rock. We value each other for social, emotional reasons; science does not tell us to do it.
But to the extent that we do have anything approaching a scientific definition of personhood, it would most likely rest in our understanding of the brain. That being the case, it's worth noting that neocortical development, which scientists believe makes emotion and cognition possible, does not begin until the late second or early third trimester of pregnancy.
