- "Plantinga (Alvin) - The Nature of Necessity" is a treasure-trove. Among its treasures are Plantinga's treatments of the problem of evil and the ontological argument, his examination of the question whether there are nonexistent objects, and his discussion of the so-called problem of trans-world identity.
- Plantinga's discussion of trans-world identity is a masterpiece of destructive philosophical analysis. Its virtues are a product of his virtues. He is a philosopher of exquisite clarity and a philosophical craftsman of the very highest order. The Nature of Necessity is founded upon a set of definitions of certain concepts that cluster round the concept of a "possible world." This set of definitions bears the unmistakable marks of Plantinga's clarity and craftsmanship. (If you think these definitions are obvious or trivial, you are the victim of an illusion: the mastery of an art consists in making the difficult look easy.) Anyone who brings Plantinga's definitions to an examination of the problem of trans-world identity will find his work half done for him. If he attends to the conceptual content of Plantinga's definientia rather than to the mental pictures (and other such distractions) that the definienda may have set drifting about in his mind, he will see that there is no problem of trans-world identity. He will find that all attempts he knows of to formulate the supposed problem are either incoherent or else have such obvious "solutions" that they do not deserve to be called problems. He will realize that it was all done with mirrors - that is, with empty words and confused pictures.
- There is, therefore, no longer any excuse for talking as if there were a "problem of trans-world identity." And yet many philosophers persist in talking as if there were a problem that went by that name1. Some of them have even read the relevant parts of The Nature of Necessity. I can think of only one explanation for this: the empty words and confused pictures are capable of exerting a firmer grip on the philosophical imagination than Plantinga has supposed. What I mean to do in this essay is to examine what are, as I see it, the most important sources of the confusions that underlie the belief that there is a problem about trans-world identity, and to try, by bringing these sources into the open, to allow us to "command a clear view" of them. My hope is that one who commands a clear view of them will be no longer subject to the confusions of which they are the source and will, as a result, see that there is no problem of trans-world identity.
- The present essay, therefore, is not a critical essay. It is not an attempt to correct Plantinga where he is wrong. It is rather an attempt to remove certain barriers to appreciating something he has to say that is right.
- Before turning to this topic, however. I shall briefly outline the set of definitions I praised a moment ago - or those of them that are relevant to our purpose. Doubtless most of the readers of this book will be familiar with them. Anyone who is not in need of a review may skip the following section. But it must be constantly borne in mind that when I use the terms I shall define in Section II. I mean by them just what I say I mean by them and nothing more than or less than or different from what I say I mean by them. If I am charged with being unduly insistent on the point. I reply that, given the history of the reception of Plantinga's arguments, I am only being prudent. Several of Plantinga's critics have not only neglected to reproduce his definitions for the benefit of their readers, but have written as if these definitions did not exist - have written as it Plantinga had never explained what he meant by such terms as "possible world" and "exists in." But one cannot discuss Plantinga's philosophy of modality2 with anyone who is unaware of Plantinga's definitions. This is not a matter of opinion: it is a simple statement of fact, the truth of which is evident to anyone who has read The Nature of Necessity. I cannot imagine what these critics supposed all those definitions were for.
Footnote 1: We are referred to "Brody (Baruch) - Identity and Essence" and a critical notice by Michael Tooley.
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