subsisting in two subjects? If it is known that two distinct subjects, each possessing a power, would undergo no diminution in power, but rather an increase, if they were conceived as a single subject possessing both powers, then the same holds for a possible effect within the power of two separate agents: if those very two agents were conceived as a single agent possessing whatever they both possessed, its power would not diminish but would increase. It is therefore clear that each could possess the power to act independently, for this is possible for it. Thus, when two agents jointly produce a single effect, it is not possible for each to be capable of producing it; rather, it is possible for them to be a single entity capable of producing it. It follows that each could be more perfect than it is and could possess a different attribute.
Now, if the essence and attributes of each can change, while it is known that it cannot perfect and change itself unaided—for, by hypothesis, it is incapable of independently producing an effect distinct from itself, and so it is all the more incapable of perfecting and changing itself—and if such a being can change and attain perfection but cannot do so by itself, then it cannot be necessarily existent in itself. Rather, it must involve contingency and dependence on another.
The hypothesis would therefore entail that it is both necessarily existent in itself and not necessarily existent in itself, making it both necessary and contingent. This is a contradiction. For whatever is necessarily existent in itself must itself suffice for the reality of its essence and attributes, without depending on another for anything pertaining to its essence, acts, or attributes, since all of these fall within what is denoted by its essence. Indeed, it must not depend on another for any of its acts or the effects it produces, for its acts, which subsist in it, fall within