Going to Article 5, he says in Article 75, Article 5 in the Thurtsiafors,

we've just talked about the fact that God changes the whole substance of bread into the substance and reality of the body of Christ in his glory,

and the substance of wine into the real presence of the substance of Christ's glorified blood, the blood

of Christ in glory. Okay. So then he's going to, and then we asked, well, how can he do that?

Well, because God is omnipotent and creator. He has infinite actual power to change the whole

substance of one reality into the whole substance of another.

So it's called conversion of substance.

He doesn't just create the body and blood of Christ to be present on the altar,

ex nihilo, from nothing, rather,

he takes one thing already existing bread and makes it the body of Christ,

one thing already existing wine and makes it to be the blood of Christ.

So then he asks here in this fifth article,

well, but don't the accidents of the bread and wine remain in the sacrament after the change?

To which the answer will be, of course they do, it's obvious we can see them.

Now, before we get into that, let's just go and talk about substance and accidents,

because that's not term knowledge that it's commonplace in our world and that we might not think about at all, so let's just talk about it for a second. The basic schema of thinking

about substance and accidents, or you can say substance and properties, stems from Aristotle,

especially in a book he wrote when he was younger, called The Categories.

And if you want to just go read about this to get a first grounding in it, you read the

categories of Aristotle. That's where it all begins. He treats it also a great deal in the metaphysics, but that's not where you start.

Usually you read the categories.

Aristotle is reacting to Plato.

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