Bernard of Chartres (see Gilson, History of Christian Philosophy in the Middle Ages, pp. 619-620 n. 21) held a view like this: There are three real (kinds of) things. They are: God, the Ideas, and matter. They are simple. Composite things seem to be real, but aren't. Nevertheless, the component elements of composite beings truly are, namely, the Ideas and matter. On going more deeply into the question, however, it turns out that the Ideas are not directly mixed with matter. Rather there are in matter certain formae nativae ("native forms", inborn or innate forms), like unto the Ideas. Compare the standard analogy of the form left in the wax by a seal-ring. The ring is like the Idea, the impression is a forma nativa. The formae nativae are diversified by their contact with matter. (You have two different impressions of the seal-ring because you have two different globs of wax.) This sounds very much like Gilbert of Poitiers: the formae nativae are all numerically distinct, and yet all alike insofar as they imitate the same Idea - come from the same seal-ring. Nevertheless, Bernard calls the Ideas "universals". (Whether they count as "universals" in the Boethian sense depends on how you interpret the Boethian requirement that universals "constitute the substance" of the things to which they are common.)
Note that in Gilbert's terminology, a "subsistence" is what Bernard of Chartres called a "native form", while a "subsistent" is what has a native form or subsistence, namely, the material composite object. Diversity is not the same as difference. Two things that are "different" must share a common genus. (species = genus + difference.) Diversity, however, does not require this, and so is the more inclusive notion. This terminological convention is found very often in the Middle Ages, although you can't rely on it. Sometimes authors will explain this terminology very nicely, and then go right ahead and say that two Aristotelian categories, for instance, are "different".
An individual is that which cannot be further divided. Gilbert says that the "subsistences (Bernard's "native forms"), by which things are, are not individuals but rather "dividuals". (I'm sorry, but that's the only way I could bring out the etymological connections here.) They are "divisible", after a fashion, insofar as they are similar to, or "con-formed" to (I have broken up the word to emphasize the sense Gilbert gives it: "of like form with") other subsistences. Thus, Socrates' humanity "con-forms" to Plato's. Notice that this is a pretty weak sense of being divisible. Gilbert's "subsistences" are definitely not divisible in the way a Boethian universal would be, or a universal according to William of Champeaux's first theory. Still, Socrates' humanity is an exact duplicate of Plato's humanity, and Gilbert apparently thinks that such "duplicability" is enough divisibility to keep a subsistence from being an "individual".
Gilbert says not only that "subsistences", by which things are, are "dividuals", but also that the things that have those subsistences, the "subsistents", are also "dividuals" (". . . not only the things that are, but also the things by which they are con-formed . . ."). In other words, Socrates and Plato are not individuals for Gilbert. They can be divided. In this case, the divisibility is not at all hard to see. Socrates and Plato are integral wholes, made up of parts, and can be divided into those parts. We don't have to think in terms of dismemberment here. It is enough to note that Socrates and Plato consist of matter together with "native forms" or "subsistences".
A true individual for Gilbert would have to be absolutely simple, not internally made up of parts, and not duplicable. Recall the remarks above about which things really are, according to Bernard of Chartres.
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Last modified: Sun Dec 27, 1998 / Jeremiah Genest