For it is evident that every being comprised within the sphere of the contingent and the finite may cease to be a whole by itself, and may contract with a nature foreign to itself a union so intimate and so strong as to depend on this foreign nature in all its functions and its states, and no longer to bear the attribution and solidarity of its actions and modifications. If, for instance, a hand detached from the whole body were to trace characters, this action would be attributed to it exclusively; it would be a subsistence, a whole by itself, and we should say, _That hand writes_. But if it should become a part of, and we should consider is as dependent on, a human nature and will, it would then lose the solidary attribution of the function of which it is the organ; and then we could no longer say, _That hand writes_; but, _That man writes_.
A contingent substance may be deprived of the possession of its subsistence by a union with a substance even inferior in nature to itself. Because its superiority over this nature would not prevent its being dependent on it in its functions and in its states, as is the case with the human soul, which presides over the body, which produces in it continual changes, and which, in spite of the excellence which distinguishes it from the mass of matter which it animates, yet depends on the body in its most intimate situations, and finds itself bowed down by the continual evil which it suffers thereby.
Hence is it that in man the possession of subsistence belongs neither to the soul nor to the body, and there is no other subsistence in him but the sum of the two natures of which he is composed, but the whole of the two extremes united together, and which is at the same time spirit and body, incorruptible and corruptible, the intelligent and the brute.
Hence, neither the soul nor the body are denominated separately by their respective functions; but it is the whole man who receives the attribution and the different appellations of the actions and states of either nature, and we say, man thinks, man walks, man wills, man grows. Consequently that axiom, _Actiones et denominationes sunt suppositorum_, Actions are to be attributed to the subsistence. We remark, in the second place, that in the infinite alone the subsistence and personality is necessary, and consequently can never be separated from him or be dependent on any other. Because in this order personality affects a nature essentially complete, total, and of its own intrinsic nature absolutely independent in its action and in its eternal and immutable state, of all external substance.