Although Duns Scotus was a scholastic
realist (as opposed to a
nominalist) in that he treated universals as real, he did not accept the Thomistic distinction between
existence and
essence. Duns Scotus followed
Aristotle in asserting that the subject matter of metaphysics is "being qua being" (
ens inquantum ens). Being in general (
ens in communi), as an univocal notion, was for him the first object of the intellect. Metaphysics includes the study of the transcendentals, so called because they transcend the division of being into finite and infinite and the further division of finite being into the ten Aristotelian categories. Being itself is a transcendental, and so are the "attributes" of being — "one", "true", and "good" — which are coextensive with being, but each add something to it. The univocity of being implies the denial of any real distinction between essence and existence.
The study of the Aristotelian categories belongs to metaphysics insofar as the categories, or the things falling under them, are studied as beings. (If they are studied as concepts, they belong instead to the logician.) There are exactly ten categories, Scotus argues. The first and most important is the category of
substance. Substances are beings in the most robust sense, since they have an independent existence (
entia per se). Beings in any of the other nine categories, called
accidents, exist in substances. The nine categories of accidents are quantity, quality, relation, action, passion, place, time, position, and state (or
habitus).
Duns elaborates a distinct view on
hylemorphism, with three important strong theses that differentiate him. He held: 1) that there exists
matter that has no form whatsoever, or prime matter, as the stuff underlying all change, against
Aquinas (cf. his
Quaestiones in Metaphysicam 7, q. 5;
Lectura 2, d. 12, q. un.), 2) that not all created substances are composites of form and matter (cf.
Lectura 2, d. 12, q. un., n. 55), that is, that purely spiritual substances do exist, and 3) that one and the same substance can have more than one substantial form — for instance, humans have at least two substantial forms, the soul and the form of the body (
forma corporeitas) (cf.
Ordinatio 4, d. 11, q. 3, n. 54). He argued for an original principle of
individuation (cf.
Ordinatio 2, d. 3, pars 1, qq. 1-6), the "
haecceity" as the ultimate unity of a unique individual (
haecceitas, an entity's 'thisness'), as opposed to the common
nature (
natura communis), feature existing in any number of individuals. For Scotus, the axiom stating that only the individual exists is a dominating principle of the understanding of reality. For the apprehension of individuals, an intuitive cognition is required, which gives us the present existence or the non-existence of an individual, as opposed to abstract cognition. Thus the human soul, in its separated state from the body, will be capable of knowing the spiritual intuitively.
The existence of God can be proven only
a posteriori, through its effects. The Causal Argument he gives for the existence of
God is particularly interesting and precise. It says that an infinity of things that are essentially ordered is impossible, as the totality of caused things that are essentially caused is itself caused, and so it is caused by some cause which is not a part of the totality, for then it would be the cause of itself; for the whole totality of dependent things is dependent, and not on anything belonging to that totality. The argument is relevant for Scotus' conception of metaphysical inquiry into being by searching the ways into which beings relate to each other.
