Thursday, June 12, 2008

yet another surprise from Leibniz

There is a funny route from Leibniz’s doctrine about subject-predicate containment to anti-essentialism (that sounds ludicrous at first, but it gets clearer when I explain what kind of anti-essentialism I mean).

Leibniz writes, “In every true affirmative proposition, whether necessary or contingent, universal or particular, the notion of the predicate is in some way included in that of the subject (FW 111-2).”

As he develops this line of thought, he ends up meaning something much stronger and controversial: (a) the complete concept of any substance S includes all the predicates P true of it; (b) the only way that one can refer to S is through its complete concept; and (c) for each S there is and can only be one complete concept (tantamount to saying that no two complete concepts do or could refer to the same thing).

This creates a prima facie problem with contingency itself. It seems to imply that if one utters truly that S is P it follows that S could not have been not-P. The “could not” is modally serious — implying that P is essential to S — implying that everything true of S is essential to S.

His famous example is the biblical character Judas. In Discourse on Metaphysics 30, he writes, “Why is it that this man will assuredly commit this sin? The reply is easy: otherwise he would not be this man.” What follows the “otherwise” Leibniz takes to be conceptually impossible — in effect, a violation of the conditions of identity.

(One could try to use contemporary counterfactual logic to claim that perhaps Judas in near worlds consistently commits the sin in question, but in worlds farther away he does not. The problem in Leibniz’s context is that this runs into constraint (c) above.)

That this really does threaten contingency is something that Leibniz tries to stave off with a strange analysis of contingency. He writes of contingent truths, “though the predicate inheres in the subject, we can never demonstrate this, nor can the proposition ever be reduced to an equation or an identity, but the analysis proceeds to infinity, only God being able to see (not the of the analysis, indeed, for there is no end, but) the nexus of terms or the inclusion of the predicate in the subject, since he sees everything that is in the series (L 265).”

This really doesn’t appear to have anything to do with whether in the nature of the case there is a distinction between features of substances that are essential or not, and this has been pointed out by many commentators on Leibniz.

He seems to be in a pretty tough spot, and this is what I meant earlier when I said of Leibniz that ironically he’s an anti-essentialist... in this specific sense: to the degree that essentialism, to be an interesting philosophical doctrine, demarcates essential properties from properties that aren’t, Leibniz doesn’t appear to have a way of marking that difference, because his philosophy implies that all properties of any S are essential to S.

John Locke, Leibniz’s great foil, is also agreed in anti-essentialism, but in the completely opposite articulation — viz., no properties, in the nature of the case, are essential to any S qua res.
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