The Scholastics had a lot of debates about distinctions, and (in particular) which sorts of things are really distinct. I will assume that most of us are familiar with the general shape of the debate and the parties involved.

Now, to my (admittedly underinformed) sense of things, it might be possible to solve the problems involved in distinguishing between a "real distinction" and a "logical distinction with a foundation in reality" if we make explicit exactly what kind of reality we're attributing to the distincta and/or exactly what sense in which the distinction is founded in reality. To that end, I submit for your consideration the following taxonomy. (Note that, as a fundamentally Scholastic project, many of the examples used will presume the truth of a broadly Scholastic ontology. Note also that I tend towards Thomism, so I will be assuming that the analogical, considered as a mode of speaking neither totally equivocal nor properly univocal, is a valid mode of language and thought.)

The Perfect Distinction holds between distincta that are literally separable - each being capable of existing apart from the other. Thus it is with the members of a family, and any other set of numerically distinct substances.

The Metaphysical Distinction holds between distincta that, while not literally separable, are at least separable by analogy. Substantial form and signate matter are distinct in such a way, as generation "brings them together" into a composite, and corruption "takes them apart." Essence and existence are metaphysically distinct as well, for they are "united" in creation and and would be "separated" in annihilation. Likewise with substance and accident, power and action, a whole and its parts, and (indeed) act and potency in general.

The Formal Distinction holds between distincta that, while not separable in any sense, are nonetheless related to one another according to some order that precludes interchangeability and interconvertibility. The Persons of the Trinity are formally distinct from One Another and from the Divine Essence, as are the soul and its faculties, the faculty of intellect from the faculty of will, genus and specific difference, and the like.

The Intentional Distinction holds between distincta that, while interchangeable and interconvertible, are distinguishable in virtue of their relations to things that are not thus interchangeable/interconvertible. So it is with being and the transcendentals (such as one, good, true, and the like); for being is that which is, simpliciter; unity, that which is, considered as related to itself; goodness, that which is, considered as related to some faculty of appetite; and truth, that which is, considered as related to some faculty of knowledge.

Finally, the Verbal Distinction holds between distincta that, while in no way differently related to other things, come to be viewed as distinct by the human mind or some other finite intellect. So it is with "human" and "rational animal."

These are, I propose, the proximate species of distinction. However, thus far, I have only illustrated each species. As Socrates emphasized, it is better to know a thing by its proper definition than by mere acquaintance with its instances. Therefore it is worth asking for the definition of each distinction in terms of genus and specific difference. To that end, I would propose the following:

The first division of distinction would be into the Intrinsic and the Extrinsic. An Intrinsic Distinction holds between distincta in virtue of their relations to each other. An Extrinsic Distinction holds between distincta that are not distinguishable in virtue of their relations to one another.

The Intentional distinction and the Verbal distinction are species of Extrinsic distinction. The Intentional distinction is an Extrinsic distinction in which the distincta are distinguishable in virtue of their relations to different objects. The Verbal distinction is an Extrinsic distinction in which the distincta are not distinguishable save as a mind conceives of them.

The Perfect distinction, the Metaphysical distinction, and the Formal distinction are species of Intrinsic distinction. We may cosider the Metaphysical and Perfect distinctions as species of a subgenra of Intrinsic distinction - one defined by the fact that the distincta are in some sense separable. For lack of a better name, we may call it a Real Distinction (though if a better designation shows up, I'll start calling it that). A Real distinction is an intrinsic distinction in which the  distincta are in some sense separable. Thus, the Perfect distinction is a real distinction in which the distincta are literally and properly separable, whereas the Metaphysical distinction is a real distinction in which the distincta are only separable by analogy. The Formal distinction is an intrinsic distinction in which the distincta are not in any sense separable, but are nevertheless related in an order that precludes interconvertibility.

Note that these species are not currently jointly exhaustive. There is no term for an intrinsic distinction in which the distincta are interconvertible but inseparable, nor is there a term for an extrinsic distinction in which the distincta do not bear different relations to other objects and yet are not distinguishable solely on the basis of the way a mind thinks about them. While I'm not convinced that there are any distincta that fall into the two "missing" distinctions, nor am I even sure that either is coherent, I don't know how to spell out my issues with such putative distinctions explicitly, nor am I comfortable with any of the quick patches which I could have used to make the current taxonomy exhaustive.

Thoughts? Objections? Suggested amendments?

Last edited by Dave (7/23/2018 10:08 pm)