AQUINAS CLARIFICATION: A friend emails this very good point (which I knew, but my poor choice of words obscured it): One minor complant, you indirectly (and I assume unintentionally) make it sound like St. Thomas was a pro-abort and that the Church has ever changed her view on the morality of abortion. You make the valid point that the Church’s understanding of abortion has developed, however, it has been constant in its opposition (i.e. Church teaching on abortion is more like teaching on homosexuality than that on slavery).

As for the church, the earliest teachings on the subject are actually among the earliest teaching. They are found in the Didache, a record of teachings of “the 12” which is contemporary with much of the New Testament (i.e. 1st century). The Didache says: “Now, this is the way of life: The second commandment of the Teaching: ‘Do not murder; do not commit adultery’; do not corrupt boys; do not fornicate; ‘do not steal’; do not practice magic; do not go in for sorcery; do not murder a child by abortion or kill a newborn infant. ”

Aquinas did say an unborn baby receives a soul forty or eighty days after conception, depending on gender. But (as you probably already know) he also said abortion is a violation of natural law and is always wrong, no matter when a soul may be infused into the developing child’s body.