[lo_zamoyski]

Indeed, the Cartesian position is not the Catholic position and, in fact, directly contradicts the Catholic position.

The soul, according to an Aristotelian-Thomistic understanding, is the form of a living thing. Form is what makes a thing what it is. If you deny form, then you deny that things have any identity whatsoever and the world becomes unintelligible. Science itself becomes impossible.

So, the form is the formal cause of a thing's identity, and so everything that exists has a formal cause, because you cannot not have something that isn't something. In living things, we call this form the soul; we sometimes say that the soul is the form of the body. Accordingly, it is absurd to think of the soul and the body to be two things (like Descartes thought), just as it is absurd to treat the spherical shape of a ball of bronze as a distinct thing from the bronze. There is no sphericial-shape-as-such or bronze-as-such as things in the world.

While Descartes denied the consciousness of non-human animals, this was never the Aristotelian-Thomist position. In fact, it is taken to be flatly wrong. So denial of the consciousness of non-human animals is not really traditional at all. It is very much modern.