-A reader asks: I think I would like clarification on this: I read Sullivan Introduction to Philosophy [available thru ITOPL], where he says that the soul is different in humans because of their intelligence and will. Isn't it the image of God in man that makes us different from the animals?
-Ite ad Thomam answers: The answer is that both (a) intellect and will, and (b) the image of God in us, make us different from the animals. But the relationship between these two differentiating principles is analogous to the relationship between philosophy and theology (or natural reason and revelation).
(a) Philosophically, we can discover through our own natural reasoning that it is our rational powers, namely, intellect and will, that make us different from the rest of the animals--and notice I say the rest of the animals, for we are animals too, the only difference being that we are rational. This is what we can know philosophically.
(b) But theologically, we can know from Divine Revelation that we are also made in the image and likeness of God. This means not only that we have intellects and wills, but that we have the capacity to be children of God through baptism and sanctifying grace. We couldn't know this philosophically, that is, through natural reasoning alone. We know this only because we have received a supernatural revelation from God.
This serves to show the similarities and differences between philosophy and theology. While they are similar insofar as they deal with many of the same subjects (ultimate questions, such as, "what is the soul?," "does God exist?"), they nevertheless are different insofar as philosophy proceeds from natural human reason and experience only, whereas theology uses these and Divine Revelation (which includes Sacred Scripture and Sacred Tradition).