We shall inquire about three [things] in this Disputation: First, whether this unity is found in all existing things; next, what it is in them; and, finally, what principle or root it has in each of them. And since the last [of these] cannot be explained in the same way (ratione) in all things, we shall inquire separately about [it in] material and spiritual substances and [in] accidents.1
1. The reason for [raising] this question can be:4 First, that although the divine nature really exists, yet it is not singular and individual, since, according to faith, it is communicable 5 to many. Second, that although each angel is an existing thing, it does not have this numerical and individual unity, but, [speaking] with precision, [it has] essential [unity],6 such as that understood by us to be in man as such.7 Therefore, [some things that exist have no numerical and individual unity].8 Proof of the minor:9 This individual unity is understood as adding something to the formal or essential [unity], by reason of which the essential nature (ratio) can be contracted and, consequently, divided into many individuals. But there is no such addition in an angel, since in it the whole essence is, as it were, separate (praecisa) and abstract, for which reason it cannot be numerically multiplied; just as, if man existed as it is conceived in abstraction, it could not be multiplied. Third, in reality man exists in Peter and Paul, and as such it is not something individual and singular. Therefore, not everything existing in the order of things has this unity.