What is the meaning and structure of individuandum?
I guess that it is an accusative gerund of unknown verb to me.
For example in this context: (Siger de Brabant, Quaestiones in metaphysicam, 1981, p.435)
quia materia non est per se sufficiens ad individuandum, dicitur quod conditiones quaedam materiae et accidentia individui, sicut esse hic et esse nunc, individuant, a quibus abstrahit ratio universalis
Siger de Brabant was one of the "Latin Averroists", who were famously criticized by such thinkers as Thomas Aquinas and Bonaventure for rationalist tendencies.
Individuation is an important philosophical concept with a wide range of uses, and basically refers to how universals (such as "dog" and "man") are instantiated in individuals (such as "Fido" and "Socrates"). Jorge E. Gracia wrote a monumental study on the issue: Individuation in Scholasticism. The Later Middle Ages and the Counter-Reformation 1150-1650
The best translation of "individuare" is "to individuate": it is a transitive verb whose subject is what makes a universal form actually individual. According to Aristotelian hylomorphism, "matter" is the usual candidate for the so-called "principium individuationis," i.e. "principle of individuation." Here is my full translation in light of that:
Since matter is not sufficient in itself to individuate, it is said that certain conditions of the matter and accidents of the individual, such as "being here" and "being now," individuate, from which universal reason abstracts.
The only part that I am hesitant about is the end: I would have expected "abstrahitur," since "ratio universalis" usually refers to a "universal account," i.e. "dog-ness." An account is abstracted, according to Scholastic terminology, and does not do the abstracting, which is the work of reason. By suspicion, which I don't have the time to confirm, is that this is a relic of Siger's Averroism: Averroes famously taught that the so-called "agent intellect," which abstracts universal concepts, is not particular to individuals, but that it is common to all men. He might plausibly refer to it as "universalis ratio," i.e. the reason shared by all people.
It looks like this word comes from a verb *indīviduāre, which I've never seen before and can't find in Lewis and Short.
So I'd say it's a one-off formation from indīviduus "indivisible, inseparable". It's hard to tell without context, but I'm guessing it means something like "to be inseparable"; the gerund is then "being inseparable".
EDIT: Now that there's context provided:
Oh, dear, this is some of the densest Latin I've had to translate! I'm pretty sure I've messed up some of the technical terms, since I'm not used to metaphysics vocabulary, but let's see here…
quia materia non est per se sufficiens ad individuandum, dicitur quod conditiones quaedam materiae et accidentia individui, sicut esse hic et esse nun, individuant, a quibus abstrahit ratio universalis
Because having substance in and of itself isn't enough to be indivisible, it's said that certain states of that substance and certain properties of an indivisible thing, like "being here" and "being now", are indivisible. From these we can derive a universal theory.
EDIT: Many thanks to Hugh for his metaphysics understanding! Updated my translation.
This seems to me to be part of the debate about Universals, and especially about Abstract nouns. An Essence which is universal, unchanging,and indivisible, is distinct from an
Accidental like colour, position, size which is variable, inconstant and can be divided up.
quia materia non est per se sufficiens ad individuandum,
Because matter is not in itself sufficient for (having indivisibility) [better] individuatation
dicitur quod conditiones quaedam materiae et accidentia individui,
it is said that certain states of matter, and (certain) accidents of an indivisible thing,
sicut esse hic et esse nun, individuant, a quibus abstrahit ration universalis.
such as here-ness and now-ness, are indivisible, from which the Universal concept abstracted.
The last four words are untranslatable: the easiest solution would be to read rationes universalis as accusative plural: 'from which he has derived the universal concepts,' or '...the universal principles.'
Because matter by itself does not suffice to render something a distinct, individual thing, it is said that certain qualities of matter and accidents (such as here-ness and now-ness) of an individual thing render that thing an individual. These qualities and accidents are the ones that universal reason does not take into account.
You have to know some Aristotelian metaphysics. Basically, an individual thing consists of a union between specific pieces of matter and a universal form. If there were no forms, the universe would just be a blob of undifferentiated matter. If there were no matter, the forms wouldn't instantiate anywhere. Universal reason is a cognitive faculty that recognizes something's form, the kind of thing that it is, based on its perceptible accidents.
But there's a further distinction between different kinds of accidents. Certain accidents are used by universal reason to determine the essence of a thing. So, when we perceive an animal with four legs, a wagging tail, saying "bark", our universal reason concludes "dog." But what differentiates two identical dogs? Other accidents, such as spatio-temporal location, which universal reason ignores (abstrahit) when determining form/type.
