Frederick Kroon

EXISTENTIALISM IN PHILOSOPHICAL LOGIC IS THE DOCTRINE THAT STATES OF AFFAIRS, PROPOSITIONS AND PROPERTIES INVOLVING OBJECTS INCLUDE THESE OBJECTS AS DIRECT CONSTITUENTS IN AT LEAST THE SENSE THAT THE NONEXISTENCE IN A WORLD w OF SOCRATES, SAY, IMPLIES THE NONEXISTENCE IN w OF SOCRATES' BEING SNUB-NOSED. JOHN POLLOCK HAS RECENTLY ARGUED (IN "THE FOUNDATIONS OF PHILOSOPHICAL SEMANTICS") THAT SUCH AN EXISTENTIALISM HARBOURS AN INCONSISTENCY. THE PRESENT PAPER REBUTS POLLOCK'S ARGUMENT BY ARGUING THAT IT DEPENDS ON A CHARACTERIZATION OF EXISTENTIALISM THAT EXISTENTIALISTS HAVE NO REASON TO ACCEPT, AND, INDEED, GOOD REASON TO REJECT

This paper deals with a philosophical question that arises within the theory of computational complexity: how to understand the notion of INTRINSIC complexity or difficulty, as opposed to notions of difficulty that depend on the particular computational model used. The paper uses ideas from Blum's abstract approach to complexity theory to develop an extensional approach to this question. Among other things, it shows how such an approach gives detailed confirmation of the view that subrecursive hierarchies tend to rank functions in terms of their intrinsic, and not just their model-dependent, difficulty, and it shows how the approach allows us to model the idea that intrinsic difficulty is a fuzzy concept.

Let g E(m, n)=o mean that n is the Gödel-number of the shortest derivation from E of an equation of the form (m)=k. Hao Wang suggests that the condition for general recursiveness mn(g E(m, n)=o) can be proved constructively if one can find a speedfunction s s, with s(m) bounding the number of steps for getting a value of (m), such that mn s(m) s.t. g E(m, n)=o. This idea, he thinks, yields a constructivist notion of an effectively computable function, one that doesn't get us into a vicious circle since we intuitively know, to begin with, that certain proofs are constructive and certain functions effectively computable. This paper gives a broad possibility proof for the existence of such classes of effectively computable functions, with Wang's idea of effective computability generalized along a number of dimensions.

This paper suggests that quantified negative existentials about fiction—statements of the form “There are some / many / etc. Fs in work W who don't exist”—offer a serious challenge to the theorist of fiction: more serious, in a number of ways, that singular negative existentials. I argue that the temptation to think that only a realist semantics of such statements is plausible should be resisted. There are numerous quantified negative existentials found in other areas that seem equally “true” but where a realist semantics imports ontological commitments that few would want to embrace. In the final part of the paper I sketch an alternative pretense account of one such quantified negative existential, and suggest that the account gives us some reason to believe that quantified negative existentials in general, including quantified negative existentials about fiction, can also be understood in pretense terms.

Consider predicates like 'is a fictional character' and 'is a mythical object'. Since their ascription entails a corresponding Negative Existential claim, call these 'NE-characterizing predicates'. Objectualists such as Parsons, Sylvan, van Inwagen, and Zalta think that NE-characterizing properties are genuine properties of genuinely non-existent objects. But how, then, to make room for statements like 'Vulcan is a failed posit' and 'that little green man is a trick of the light'? The predicates involved seem equally NE-characterizing yet on the surface fail to mark a genuine property o f things. Instead, the truth of such predications strongly supervenes on types of referential failure. Kendall Walton's anti-objectualist account of talk about fiction provides a neat solution to this supervenience problem by invoking special games of make-believe. The present paper claims that while Walton's view thereby gains an important advantage over objectualism, the solution faces problems of its own. The rest of the paper desribes another solution, one that assigns a large role to the idea of metaphor.

This article argues for a certain picture of the rational formation of conditional intentions, in particular deterrent intentions, that stands in sharp contrast to accounts on which rational agents are often not able to form such intentions because of what these enjoin should their conditions be realized. By considering the case of worthwhile but hard-to-form deterrent intentions (the threat to leave a cheating partner, say), the article argues that rational agents may be able to form such intentions by first simulating psychological states in which they have successfully formed them and then bootstrapping themselves into actually forming them. The article also discusses certain limits imposed by this model. In particular, given the special nature of deterrent intentions (e.g. the ones supposedly involved in nuclear deterrence), there is good reason to think that these must remain inaccessible to fully rational and moral agents