Do whales have souls and if so what follows ? How would Catholic theology have to change if it was discovered that whales were as rational as you or I ? If whales have souls can they become Catholics ?

For a traditional Catholic, to have a soul, in latin anima, is to be animate, to be alive. Having a soul is having a certain form, a certain organisation such that one can move oneself. One part moves another so that the whole moves itself. This self-moving quality, shown in the processes of nutrition, growth and reproduction, is common to all living things. To be alive is to have a soul. St. Thomas Aquinas would affirm that all living things from cabbages to whales, so long as they were alive, were so in virtue of a soul.

This broadly speaking, is the scriptural view, though it is often obscured by translation. In Genesis 1:20 God says,‘Let the waters bring forth swarms of living creatures’. In Genesis 2:7 God breathes into the nostrils of the man so that he becomes a ‘living being’. In both cases the word nephesh is used which in other places we would translate soul. So the waters brought forth swarms of living souls, and Adam became a living soul. Plants are a bit of a borderline case, for though clearly alive they are not very lively. However, with this small qualification, hebrew Old Testament, greek New Testament, and latin scholastic theology would agree.