Online research in philosophy

Universals: Loux, M. J. The existence of universals. Russell, B. The world of universals. Quine, W. V. O. On what there is. Pears, D. F. Universals. Strawson, P. F. Particular and general. Wolterstorff, N. Qualities. Bambrough, R. Universals and family resemblances. Donagan, A. Universals and metaphysical realism. Sellars, W. Abstract entities. Wolterstorff, N. On the nature of universals.--Particulars: Loux, M. J. Particulars and their individuation. Black. M. The identity of indiscernibles. Ayer, A. J. The identity of indiscernibles. O'Connor, D. J. The identity of indiscernibles. Allaire, E. B. Bare particulars. Chappell, V. C. Particulars re-clothed. Allaire, E. B. Another look at bare particulars. Meiland, J. W. Do relations individuate? Long, D. C. Particulars and their qualities. Copi, I. Essence and accident. Chandler, H. S. Essence and accident. Plantinga, A. World and essence.

Faced with strong arguments to the effect that Leibniz''sPrinciple of the Identity of Indiscernibles (PII) is not a necessary truth, many supporters of the Principle have staged a strategic retreat to the claim that it is contingently true in this, the actual, world. The purpose of this paper is to examine the status of the various forms of PII in both classical and quantum physics, and it is concluded that this latter view is at best doubtful, at worst, simply wrong.

The view that numerical difference entails qualitative difference has come under attack from various quarters. One classical attack, advanced by Black, involves possible worlds which are symmetrical. In a symmetrical world, it is claimed, the identity of indiscernibles is false. I argue that such attacks are mistaken, basically because they confuse epistemological issues (such as, how to specify a quality difference) with ontological ones (such as, whether there is such a quality difference). In brief, though there may be some reasons for doubting the necessity of the Identity of lndiscernibles, the possibility of a symmetrical world is not one of them.

I give a critique of the argument against the Identity of Indiscernibles found in Max Black's dialogue "The Identity of Indiscernibles". I begin by postulating and giving existence and individuation conditions for actually existent thought experiment characters on analogy with fictional characters as postulated in Peter van Inwagen's "Creatures of Fiction". I then show that Black's two-spheres thought experiment raises not one but two discernibility questions: 1) Is it true in the two-spheres thought experiment that there exist two indiscernible spheres? NO. 2) Is it true in the actual world that there are two indiscernible sphere-characters? YES.

In this paper I reconstruct Leibniz's argument for the Identity of Indiscernibles in his *Primary Truths*. I criticise the alternative interpretation put forward by Cover and O'Leary-Hawthorne and defend my own interpretation, both on philosophical and hermeneutical grounds.

The Identity of Indiscernibles is the principle that there cannot be two individual things in nature that are qualitatively identical. The principle is not exactly popular. Michael Della Rocca tries to resurrect it by arguing that we must accept this principle, for otherwise we cannot explain the impossibility of completely overlapping indiscernible objects of the same kind that share all their parts and exist in the same place at the same time. I try to show that his argument goes wrong: we need not embrace the identity of indiscernibles to deal with the co-location problem.

Recently, several authors have claimed to have found graph-theoretic counterexamples to the Principle of the Identity of Indiscernibles. In this paper, I argue that their counterexamples presuppose a certain view of what unlabeled graphs are, and that this view is optional at best.

In ‘Two Spheres, Twenty Spheres, and the Identity of Indiscernibles,’ Della Rocca argues that any counterexample to the PII would involve ‘a brute fact of non-identity [. . .] not grounded in any qualitative difference.’ I respond that Adams's so-called Continuity Argument against the PII does not postulate qualitatively inexplicable brute facts of identity or non-identity if understood in the context of Kripkean modality. One upshot is that if the PII is understood to quantify over modal as well as non-modal properties, the qualitative explicability of numerical distinctness requires not the PII but a principle of the identity of necessary indiscernibles.

I argue that the standard counterexamples to the identity of indiscernibles fail because they involve a commitment to a certain kind of primitive or brute identity that has certain very unpalatable consequences involving the possibility of objects of the same kind completely overlapping and sharing all the same proper parts. The only way to avoid these consequences is to reject brute identity and thus to accept the identity of indiscernibles. I also show how the rejection of the identity of indiscernibles derives some of its support from its affinity with a Kripkean account of trans-world identity and theories of direct reference.