B. Scotus’ own Opinion

194. I say to the question, therefore, that since a triple action can be posited to belong to accidents, namely one with respect to generating substance and two with respect to causing accidents (one with respect to sensation, the other real as to a passive thing that really has the contrary [accident]) - the first can in no way belong to a separated accident, not even instrumentally, as already proved [nn.191-193] - and this when taking ‘instrument’ for any cause that attains the end of the principal agent, whether for a second cause properly speaking, or for a part through which the whole acts, or for what then receives the active form by which it acts, or for what receives motion alone as an effect on the way to the principal effect (these ways of taking ‘instrument’ are plain above [refs. in n.192]). For in all these ways it is required that that of which it is the instrument concur in its own order as causer; and, when it does not exist, nothing causes in any order of causing.

195. But besides these modes, an instrument is called a cause that precedes as dispositive for the term [Ord. IV d.6 n.117], and this even though it have the dispositive action in its own virtue; and in this way it is very possible for an accident to be the instrument of substance, because it can cause an action dispositive for the term of the agent’s substance. But not even in this way can an accident be an instrument of substance in the issue at hand, because a substance that does not exist induces no term, nor can induce any term, at the end of the alteration caused by the accidents.