Thomas Aquinas was correct that the unborn receive their souls at conception; he was merely mistaken on when conception was finished, due to the science available. As modern medicine has shown, conception in humans occurs almost instantaneously, as soon as the sperm and the ovum unite. This may occur as soon as twenty minutes after the marital act.  According to the Catholic Source:  https://www.catholic.com/magazine/print-edition/when-babies-get-their-souls They also said,  "Aquinas and a few other medieval Western writers held the forty-to-ninety-day conception theory, but the biological discoveries of the nineteenth century proved it wrong. The view provides little comfort for abortion advocates today for a variety of reasons. It was based on primitive science. It draws a distinction between males and females that many today would regard as sexist. It was held by only a few writers. No single theologian (even Aquinas) speaks for the Church. The writers who favor...