Achille C. Varzi

This volume aims to offer an up-to-date indication of the on-going debate on the nature of logic. The focus is on questions pertaining to the existence and individuation of clear boundaries delineating the concerns of logic: What is their distinctive character? What makes logic a subject of its own, separate from (and generally in the background of) the concerns of other disciplines? What is it for an expression to be a logical constant? Or, perhaps equivalently, what is it for an operation or a relation to be logical? Can these questions be addressed in a general setting, or are they intrinsically unanswerable except within specific frameworks of reference (e.g., a language, or a conceptual scheme)? How are they to be addressed—are they semantic, syntactic, pragmatic? And how do semantics, syntax, or pragmatics contribute to our understanding of these questions? Are the answers fully captured by extant systems of logic? Contributors: E. Bencivenga, J. van Benthem, D. van Dalen, M. García-Carpintero and M. Pérez Otero, A. P. Hazen, A. Koslow, G. Priest, G. Sher.

We tend to talk about (refer to, quantify over) parts in the same way in which we talk about whole objects. Yet a part is not something to be included in an inventory of the world over and above the whole to which it belongs, and a whole is not something to be included in the inventory over and above its constituent parts. This paper is an attempt to clarify a way of dealing with this tension which may be labeled the Minimalist View: An element in the field of a part-whole relation is to be included in an inventory of the world if and only if it does not overlap any distinct element that is itself included in the inventory.

Analyses, in the simplest form assertions that aim to capture an intimate link between two concepts, are viewed since Russell's theory of definite descriptions as analyzing descriptions. Analysis therefore has to obey the laws governing definitions including some form of a Substitutivity Principle (SP). Once (SP) is accepted the road to the paradox of analysis is open. Popular reactions to the paradox involve the fundamental assumption (SV) that sentences differing only in containing an analysandum resp. an analysans express the same proposition, because analysandum and analysans are the same entity. Following suggestions of Gupta and Belnap it is argued that (SV) should be rejected.

The so-called "argument from vagueness", the clearest formulation of which is to be found in Ted Sider’s book Four-dimensionalism, is arguably the most powerful and innovative argument recently offered in support of the view that objects are four-dimensional perdurants. The argument is defective--I submit--and in a number of ways that is worth looking into. But each "defect" corresponds to a model of change that is independently problematic and that can hardly be built into the common-sense picture of the world. So once all the gaps of the argument are filled in, the three-dimensionalist is left with the burden of a response that cannot rely on a passive plea for common sense. The argument is not a threat to common sense as such; it is a threat to the three-dimensionalist faithfulness to common sense.

I articulate and the defend the following two claims: (i) it is a mistake to think that the structure of the world should mirror the structure of the theories by which we represent it, and through which we try to decipher it, simply because those theories appear to work; (ii) among the most deplorable consequences of this mistake is the widespread tendency to think that there must be a plurality of realities, or several different and irreducible levels of a stratified reality, merely because our credo includes a plurality of theories each of which appears to be as important and trustworthy as it is irreducible to (if not overtly in conflict with) the others.

Convexity predicates and the convex hull operator continue to play an important role in theories of spatial representation and reasoning, yet their first-order axiomatization is still a matter of controversy. In this paper, we present a new approach to adding convexity to mereotopological theory with boundary elements by specifying first-order axioms for a binary segment operator s. We show that our axioms yields a convex hull operator h that supports, not only the basic properties of convex regions, but also complex properties concerning region alignment. We also argue that h is stronger than convex hull operators from existing axiomatizations and show how to derive the latter from our axioms for s.

There are more things between heaven and earth than are dreamt of in our philosophy, says Hamlet. Right. But there are also philosophies that have dreamt of things that are neither here nor there, as Goodman says. There is a danger of suffering from ontological myopia just as there is a danger of suffering from ontological allucination. This paper is about some basic strategies that are available to (or have been elaborated by) philosophers to steer clear of both dangers in their efforts to draw up a good inventory of what there is.

The Doctrine of Potential Parts says that proper undetached parts are merely potential entities, entities that do not exist but would exist if they were detached from the rest. They are just aspects of the whole to which they belong, ways in which the whole could be broken down, and talk of such parts is really just talk about the modal properties of the whole. Here I offer a reconstruction of this doctrine and present an argument to illustrate its hidden kinship with another, parallel but independent doctrine Doctrine of Potential Wholes. According to this second doctrine, disconnected wholes (i.e., wholes that are not in one piece) are in turn potential entities, entities that do not exist but would exist if their parts were suitably conjoined.

In ‘Towards a Solution to the Sorites Paradox’, Graham Priest gives us a new account of the sorites based on fuzzy logic. The novelty lies in the suggestion that truth-value assignments should themselves be treated as fuzzy objects, i.e., objects about which we can make fuzzy identity statements. I argue that Priest’s solution does not have the explanatory force that Priest advocates. That is, it does not explain why we find the existence of a cut-off point counter-intuitive. I also argue that this sort of explanation calls for a general theory that goes beyond the special case of linguistic vagueness, for the phenomenon is at bottom not linguistic.

Just as ontology developed over the centuries as part of philosophy, so in recent years ontology has become intertwined with the development of the information sciences. Researchers in various fields have come to realize that a solid foundation for their projects calls for an explicit theorization of the types of entities and relations that make up their respective domains of inquiry, and as the need for integrating such projects arises, so does the need to identify common ontological principles over ad hoc, case-based solutions. This volume collects the papers presented at the third international conference devoted to current research in this area, including invited papers by P. Gärdenfors and A. L. Thomasson.

There are conflicting intuitions concerning the status of a boundary separating two adjacent entities (or two parts of the same entity). The boundary cannot belong to both things, for adjacency excludes overlap; and it cannot belong to neither, for nothing lies between two adjacent things. Yet how can the dilemma be avoided without assigning the boundary to one thing or the other at random? Some philosophers regard this as a reductio of the very notion of a boundary, which should accordingly be treated a mere façon de parler. In this paper I resist this temptation and examine some ways of taking the puzzle at face value within a realist perspective—treating boundaries as ontologically on a par with (albeit parasitic upon) extended parts.

Might we some day be in a position to move about in time, just as we can already move about in space? Today, few would question that deliberate change in temporal location is logically possible. There is no contradiction in the thought that Tim could step into a time machine and travel backwards to visit his grandfather, or forwards to visit his grandchildren. That is, there is no contradiction provided that we take time travel to involve influencing the course of history rather than changing it. But is time travel metaphysically possible? Is there a genuinely possible world—as opposed to a merely coherent scenario—in which one can freely change one’s location in time? Here is where puzzlement and bewilderment lead to philosophical controversy. For the answer depends on one’s views concerning a wide range of other matters, and such views are themselves the subject of major philosophical controversy. Consider

Assuming that events form a genuine ontological category, shall we say that a good inventory of the world ought to include “negative” events—failures, omissions, things that didn’t happen—along with positive ones? I argue that we shouldn’t. Talk of non-occurring events is like talk of non-existing objects and should not be taken at face value. We often speak as though there were such things, but deep down we want our words to be interpreted in such a way as to avoid serious ontological commitment.

An overview of the way I picture the amorphous world we live in, built around my comments and responses to nine festschrift essays by A. Borghini (on the Fedro metaphor and the art of butchery), F. Calemi (on the predication principle and metalinguistic nominalism), C. Calosi (on the argument from mereological universalism to extensonality), E. Casetta (on the role of “monsters” in the realism/antirealism debate), V. Giardino (on inductive reasoning, spatial representation, and problem solving), P. Graziani (on mereological notation), P. Pedrini (on the distinction between natural and artificial boundaries), D. Santoro (on causation by omission), and G. Torrengo (on absolute vs. relational space and the problem of incongruent counterparts).

What sort of logic do we get if we adopt a supervaluational semantics for vagueness? As it turns out, the answer depends crucially on how the standard notion of validity as truth preservation is recasted. There are several ways of doing that within a supervaluational framework, the main alternative being between “global” construals (e.g., an argument is valid iff it preserves truth-under-all-precisifications) and “local” construals (an argument is valid iff, under all precisifications, it preserves truth). The former alternative is by far more popular, but I argue in favor of the latter, for (i) it does not suffer from a number of serious objections, and (ii) it makes it possible to restore global validity as a defined notion.

In previous work, I introduced a complete axiomatization of classical non-tautologies based essentially on Łukasiewicz’s rejection method. The present paper provides a new, Hilbert-type axiomatization (along with related systems to axiomatize classical contradictions, non-contradictions, contingencies and non-contingencies respectively). This new system is mathematically less elegant, but the format of the inferential rules and the structure of the completeness proof possess some intrinsic interest and suggests instructive comparisons with the logic of tautologies.

Remember the story of the most-most? It’s the story of that club in New York where people are the most of every type. There is the hairiest bald man and the baldest hairy man; the shortest giant and the tallest dwarf; the smartest idiot and the stupidest wise man. They are all there, including honest thieves and crippled acrobats. On Saturday night they have a party, eat, drink, dance. Then they have a contest. “And if you can tell the hairiest bald man from the baldest hairy man—we are told—you get a prize.”.

David Lewis has argued that impossible worlds are nonsense: if there were such worlds, one would have to distinguish between the truths about their contradictory goings-on and contradictory falsehoods about them; and this--Lewis argues--is preposterous. In this paper I examine a way of resisting this argument by giving up the assumption that ‘in so-and-so world’ is a restricting modifier which passes through the truth-functional connectives The outcome is a sort of subvaluational semantics which makes a contradiction ‘A & ~A’ false even when both ‘A’ and ‘~A’ are true, just as supervaluational semantics makes a tautology ‘A v ~A’ true even when neither ‘A’ nor ‘~A’ are. Connections with discussive logics and complications of the account are discussed, and some general morals are drawn.

The “Game of the Rule” is easy enough: I give you the beginning of a sequence of numbers (say) and you have to figure out how the sequence continues, to uncover the rule by means of which the sequence is generated. The game depends on two obvious constraints, namely (1) that the initial segment uniquely identify the sequence, and (2) that the sequence be non-random. As it turns out, neither constraint can fully be met, among other reasons because the relevant notion of randomness is either vacuous or undecidable. This may not be a problem when we play for fun. It is, however, a serious problem when it comes to playing the game for real, i.e., when the player to issue the initial segment is not one of us but the world out there, the sequence consisting not of numbers (say) but of the events that make up our history. Moreover, when we play for fun we know exactly what initial segment to focus on, but when we play for real we don’t even know that. This is the core difficulty in the philosophy of the inductive sciences.