Philosophical logic has its problem-children; and among these the Principle of Substitutivity of codesignating expressions — the linguistic spawn of Leibniz's law—has achieved a place of prominence. It has become increasingly apparent that a certain style of linguistic analysis, which seeks to impose formal regimentation ruled by the constraints of classical quantification theory, does not yield results with the kind of uniformity and elegance one should hope for from a satisfyi.ng theory. The root of the difficulty, I believe, bears upon (...) the answers to fundamental questions concerning the nature of cognitive agents and the purposes which their use of language is designed to further. If this is the case, one might expect to find some of the trouble surfacing at precisely those points where the language is used to convey information about the cognitive activities associated with the use of language by such agents. So it is.The central problem of this essay is the interpretation of referential expressions in statements involving propositional attitudes, with the focus on belief contexts. But I shall begin by placing the discussion within a broader theoretical framework. (shrink)

The aim of this paper is to show that it is not irrational to doubt one’s own existence, even in the face of introspective evidence to the effect that one is currently in a certain mental state. For this purpose, I will outline a situation in which I do not exist, but which cannot be ruled out on the basis of any evidence available to me—including introspective evidence about my current mental states. I use this ‘superskeptical scenario,’ as I will (...) call it, to formulate an argument to the conclusion that I do not know that I exist. In order to substantiate my argument, I draw upon Terence Parsons’ theory of non-existent objects. I conclude that, inasmuch as Parsons’ theory is reasonable, doubts about one’s own existence are reasonable as well. (shrink)

Are there nonexistent objects, i.e., objects that do not exist? Some examples often cited are: Zeus, Pegasus, Sherlock Holmes, Vulcan (the hypothetical planet postulated by the 19th century astronomer Le Verrier), the perpetual motion machine, the golden mountain, the fountain of youth, the round square, etc. Some important philosophers have thought that the very concept of a nonexistent object is contradictory (Hume) or logically ill-formed (Kant, Frege), while others (Leibniz, Meinong, the Russell of Principles of Mathematics) have embraced it wholeheartedly. (...) This entry is an examination of the many questions which arise in connection with the view that there are nonexistent objects. The following are particularly salient: What reasons are there (if any) for thinking that there are nonexistent objects? If there are nonexistent objects, then what kind of objects are they? How can they be characterized? Is it possible to provide a consistent theory of nonexistent objects? What is the explanatory force of a consistent theory of nonexistent objects (if such a thing is possible)? (shrink)

The logic of fiction has been a stand-alone research programme only since the early 1970s.1 It is a fair question as to why in the first place fictional discourse would have drawn the interest of professional logicians. It is a question admitting of different answers. One is that, since fictional names are “empty”, fiction is a primary datum for any logician seeking a suitably comprehensive logic of denotation. Another answer arises from the so-called incompleteness problem, exemplified by the fact (or (...) apparent fact) that some fictional sentences – think of “Sherlock Holmes’ mother was nick-named ‘Polly’” − are neither true nor false. These are sentences to command the attention of logicians who work on non-bivalent logics. A further spur to logical engagement is the supposed fictionality of certain kinds of ideal models in science and certain classes of mathematical objects. No doubt, there are other features of fictional discourse that provide the logician with a natural entré, but perhaps it would also be correct to say that the fiction’s biggest draw for logicians is that our quite common beliefs about the fictional constitute what Nicholas Rescher calls “aporetic clusters”, so named after the Latinized Greek aporos for “impassable”.2 An aporetic cluster is a set of claims such that.. (shrink)