We know a soul was there from conception, but what kind of soul, a vegetative soul (material soul) a sentient soul (a physical soul) or a spiritual soul (a rational soul) We also know that as the baby develops, he shows signs of intelligence (sense knowledge, animal knowledge?) or rational knowledge(spiritual knowledge, the knowledge of ideas) We do know at some point of development that rational activity takes place, and that is because rational intelligence is what differentiates a human from an animal, even humans are called rational animals. Intelligence (rational) is one of the faculties of a spiritual soul, the ability to understand, to know, and to know that we know, a spiritual act.
It becomes apparent that there is progressive development in humans from the union of sperm and the ovum, so no matter when the rational soul is infused, these preliminary steps must take place for the existence of a human. Since there is an orderly and intelligent progression in human development from conception to maturity, there is an ordering principle of activity, this principle is called “the soul” So to interfere with this order from conception on, is to kill or abort a human being in it’s stage of progression. Humans beget humans, not dogs, cats or some other animal, this is an empirical fact. Those that abort try to rationalize, or justify their acts by saying that the fetus, or conceptus is not fully human, or not human at all, but a parasite, or just an animal leaching life from its mother. Another favorite excuse used to justify abortion is that a baby is not human until it takes its first breadth, they confuse life with one of its functions (the cause is being confused with one of it’s effects)