Exposition of the Faith

For although there is no nature without subsistence, nor essence apart from person (since in truth it is in persons and subsistences that essence and nature are to be contemplated), yet it does not necessarily follow that the natures that are united to one another in subsistence should have each its own proper subsistence. For after they have come together into one subsistence, it is possible that neither should they be without subsistence, nor should each have its own peculiar subsistence, but that both should have one and the same subsistence. For since one and the same subsistence of the Word has become the subsistence of the natures, neither of them is permitted to be without subsistence, nor are they allowed to have subsistences that differ from each other, or to have sometimes the subsistence of this nature and sometimes of that, but always without division or separation they both have the same subsistence— a subsistence which is not broken up into parts or divided, so that one part should belong to this, and one to that, but which belongs wholly to this and wholly to that in its absolute entirety. For the flesh of God the Word did not subsist as an independent subsistence, nor did there arise another subsistence besides that of God the Word, but as it existed in that it became rather a subsistence which subsisted in another, than one which was an independent subsistence. Wherefore, neither does it lack subsistence altogether, nor yet is there thus introduced into the Trinity another subsistence.