On Being and Essence

And it was all in the distinction of essence and existence in Aquinas.

And Aquinas wrote a little treatise when he was in his early 30s called De Ente Essentia, On Being in Essence.

And in chapter four of it, he's been looking at what essence is.

And essence is simply the definition of the thing.

So you're correct, of course, to lay the finger on the distinction between essence and existence, as Sartre does, but as St. Thomas also does, right? So Étienne Gilson, the great French Thomist, believed that Thomas was the first great existentialist theologian in that he was a theologian who, was deeply concerned with the nature of existence as such.

And, of course, Thomas has this magnificent treatise, De Ente et Essentia, On Being and Essence, that is not an easy read, but an essential one for Thomistic metaphysics and ontology.

Now, is it appropriate for Catholics to read and make use of atheism, of atheistic philosophy like Sartre? Absolutely, of course it's appropriate, because Catholics are about Christianizing, baptizing, as it were, the good things of the world, of which French existentialist atheists are a part.

And you can be a French existentialist and have genuine insights about that can be called by Catholic thinkers.