Exposition of the Faith

The natures of the Lord are neither one body nor one superficies, nor one line, nor place, nor time, so as to be brought under a continuous quantity: for these are the things that are reckoned continuously. But the natures of the Lord are united without confusion in respect of subsistence, and are divided without separation according to the method and manner of difference. And according to the manner in which they are united they are not enumerated. For we do not say that the natures of Christ are two subsistences or two in respect of subsistence.

But according to the manner in which they are divided without division, are they enumerated. For there are two natures according to the method and manner of difference. For being united in subsistence and permeating one another they are united without confusion, neither having been changed into the other, but each preserving its own natural difference even after the union. For that which is created remained created, and that which is uncreated, uncreated. By the manner of difference, then, and in that alone, they are enumerated, and thus are brought under discontinuous quantity.

For things which differ from each other in no respect cannot be enumerated, but just so far as they differ are they enumerated; for instance, Peter and Paul are not enumerated in those respects in which they are one: for being one in respect of their essence they are not two natures nor are they so spoken of. But inasmuch as they differ in subsistence they are spoken of as two subsistences. So that difference is the cause of number.