This paper argues that the theory of structured propositions is not undermined by the Russell-Myhill paradox. I develop a theory of structured propositions in which the Russell-Myhill paradox doesn't arise: the theory does not involve ramification or compromises to the underlying logic, but rather rejects common assumptions, encoded in the notation of the $\lambda$-calculus, about what properties and relations can be built. I argue that the structuralist had independent reasons to reject these underlying assumptions. The theory is given (...) both a diagrammatic representation, and a logical representation in a novel language. In the latter half of the paper I turn to some technical questions concerning the treatment of quantification, and demonstrate various equivalences between the diagrammatic and logical representations, and a fragment of the $\lambda$-calculus. (shrink)
This paper argues that attitudinal objects, entities of the sort of John's judgment, John's thought, and John's claim, should play the role of propositions, as the cognitive products of cognitive acts, not the acts themselves.
Propositions are traditionally regarded as performing vital roles in theories of natural language, logic, and cognition. This chapter offers an opinionated survey of recent literature to assess whether they are still needed to perform three linguistic roles: be the meaning of a declarative sentence in a context, be what is designated by certain linguistic expressions, and be the content of illocutionary acts. After considering many of the relevant choice-points, I suggest that there remains a linguistic basis for propositions, (...) but not for some of the traditional reasons. (shrink)
I formulate an account, in terms of essence and ground, that explains why atomic Russellian propositions have the truth conditions they do. The key ideas are that (i) atomic propositions are just 0-adic relations, (ii) truth is just the 1-adic version of the instantiation (or, as I will say, holding) relation (Menzel 1993: 86, note 27), and (iii) atomic propositions have the truth conditions they do for basically the same reasons that partially plugged relations, like being an (...) x and a y such that Philip gave x to y, have the holding conditions they do. The account is meant to be mainly of intrinsic interest, but I hope that it goes some distance toward answering an objection to classical theories of propositions put forward by King (2014), who writes that ‘since the classical conception of propositions as things that have truth conditions by their very natures and independently of minds and languages is incapable of explaining how or why propositions have truth conditions, it is unacceptable’ (2014: 47). Propositions do have their truth conditions ‘by their very natures’ and ‘independently of minds and languages’. But a fact about a given entity can hold by the very nature of that entity without being a fundamental fact. I argue that this is plausibly the case for atomic Russellian propositions and the facts about their truth conditions. A fact about the truth conditions of such a proposition holds by the very nature of the given proposition but is metaphysically grounded in facts about that proposition’s parts and their essences. If my account is correct, then the supposedly intractable problem of explaining why the given propositions have the truth conditions they do reduces to the problem of explaining why relations have the holding essences they do, which few seem to have found worrisome . (shrink)
Do Russellian propositions have their constituents as parts? One reason for thinking not is that if they did, they would generate apparent counterexamples to plausible mereological principles. As Frege noted, they would be in tension with the transitivity of parthood. A certain small rock is a part of Etna but not of the proposition that Etna is higher than Vesuvius. So, if Etna were a part of the given proposition, parthood would fail to be transitive. As William Bynoe has (...) noted (speaking of facts rather than propositions), they would seem to violate certain supplementation principles. Consider the singular proposition, concerning identity, that it is identical with itself. Given the relevant form of Russellianism, this proposition would have identity as a proper part, but it would not have any parts disjoint from identity, and indeed it would not have even a single pair of disjoint parts, in violation of various supplementation principles. This chapter offers a unified solution to the problems about transitivity and supplementation. One key ingredient in the solution is the view that parthood is a four-place relation expressed by ‘x at y is a part of z at w’. Another key ingredient is the view that the semantic contents of predicates and sentential connectives have ‘slots’ or ‘argument positions’ in them. (Both ingredients are independently motivated elsewhere.) Four-place analogues of the transitivity and supplementation principles are set out, and it is argued that these are not threatened by the examples from Frege and Bynoe. (shrink)
Accounts of propositions as sets of possible worlds have been criticized for conflating distinct impossible propositions. In response to this problem, some have proposed to introduce impossible worlds to represent distinct impossibilities, endorsing the thesis that impossible worlds must be of the same kind; this has been called the parity thesis. I show that this thesis faces problems, and propose a hybrid account which rejects it: possible worlds are taken as concrete Lewisian worlds, and impossibilities are represented as (...) set-theoretic constructions out of them. This hybrid account (1) distinguishes many intuitively distinct impossible propositions; (2) identifies impossible propositions with extensional constructions; (3) avoids resorting to primitive modality, at least so far as Lewisian modal realism does. (shrink)
Propositions play a central role in contemporary semantics. On the Russellian account, propositions are structured entities containing particulars, properties and relations. This contrasts sharply with the sets-of-possible-worlds view of propositions. I’ll discuss how to extend the sets-of-worlds view to accommodate fine-grained hyperintensional contents. When this is done in a satisfactory way, I’ll argue, it makes heavy use of entities very much like Russellian tuples. The two notions of proposition become inter-definable and inter-substitutable: they are not genuinely distinct (...) accounts of how propositions represent what they represent. Semantic theorists may move freely between the two conceptions of what propositions are. Nevertheless, the two approaches give different accounts of the metaphysical nature of propositions. I argue that the sets-of-worlds view provides an adequate account of the nature of propositions, whereas the Russellian view cannot. (shrink)
Propositions are often aligned with truth-conditions. The view is mistaken, since propositions discriminate where truth conditions do not. Propositions are hyperintensional: they are sensitive to necessarily equivalent differences. I investigate an alternative view on which propositions are truthmaker conditions, understood as sets of possible truthmakers. This requires making metaphysical sense of merely possible states of affairs. The theory that emerges illuminates the semantic phenomena of samesaying, subject matter, and aboutness.
The object of this paper is to sketch an approach to propositions, meaning and names. The key ingredients are a Twin-Earth-inspired distinction between internal and external meaning, and a middle-Wittgenstein-inspired conception of internal meaning as role in language system. I show how the approach offers a promising solution to the problem of the meaning of proper names. This is a plea for a neglected way of thinking about these topics.
It is our contention that an ontological commitment to propositions faces a number of problems; so many, in fact, that an attitude of realism towards propositions—understood the usual “platonistic” way, as a kind of mind- and language-independent abstract entity—is ultimately untenable. The particular worries about propositions that marshal parallel problems that Paul Benacerraf has raised for mathematical platonists. At the same time, the utility of “proposition-talk”—indeed, the apparent linguistic commitment evident in our use of 'that'-clauses (in offering (...) explanations and making predictions)—is also in need of explanation. We account for this with a fictionalist analysis of our use of 'that'-clauses. Our account avoids certain problems that arise for the usual error-theoretic versions of fictionalism because we apply the notion of semantic pretense to develop an alternative, pretense-involving, non-error-theoretic, fictionalist account of proposition-talk. (shrink)
The topic of this article is the ontology of practical reasons. We draw a critical comparison between two views. According to the first, practical reasons are states of affairs; according to the second, they are propositions. We first isolate and spell out in detail certain objections to the second view that can be found only in embryonic form in the literature – in particular, in the work of Jonathan Dancy. Next, we sketch possible ways in which one might respond (...) to each one of these objections. A careful evaluation of these complaints and responses, we argue, shows that the first view is not as obviously compelling as it is thought by Dancy. Indeed, it turns out that the view that practical reasons are propositions is by no means unworkable and in fact, at least under certain assumptions, explicit considerations can be made in favour of a propositional construal of reasons. (shrink)
In this paper, I discuss two concerns for pluralist truth theories: a concern about a key detail of these theories and a concern about their viability. The detail-related concern is that pluralists have relied heavily upon the notion of a domain, but it is not transparent what they take domains to be. Since the notion of a domain has been present in philosophy for some time, it is important for many theorists, not only truth pluralists, to be clear on what (...) domains are and what work they can do. The viability-related concern is that it’s not clear how a pluralist truth theory could explain the truth-conditions of mixed atomic propositions. To address this concern, truth pluralists should recognize something to which they have not been sufficiently attentive: that some atomic propositions belong to more than one domain. But, recognizing this requires rethinking the relationships between the nature of propositions, their membership in domains, and their truth. I address these issues and propose an understanding of them that is preferable to the best existing account of them, that offered by Michael Lynch. (shrink)
Speaks defends the view that propositions are properties: for example, the proposition that grass is green is the property being such that grass is green. We argue that there is no reason to prefer Speaks's theory to analogous but competing theories that identify propositions with, say, 2-adic relations. This style of argument has recently been deployed by many, including Moore and King, against the view that propositions are n-tuples, and by Caplan and Tillman against King's view that (...)propositions are facts of a special sort. We offer our argument as an objection to the view that propositions are unsaturated relations. (shrink)
Philosophers often talk about the things we say, or believe, or think, or mean. The things are often called ‘propositions’. A proposition is what one believes, or thinks, or means when one believes, thinks, or means something. Talk about propositions is ubiquitous when philosophers turn their gaze to language, meaning and thought. But what are propositions? Is there a single class of things that serve as the objects of belief, the bearers of truth, and the meanings of (...) utterances? How do our utterances express propositions? Under what conditions do two speakers say the same thing, and what (if anything) does this tell us about the nature of propositions? There is no consensus on these questions—or even on whether propositions should be treated as things at all. During the second Propositions and Same-Saying workshop, which took place on July 19–21 2010 at the University of Sydney, philosophers debated these (and related) questions. The workshop covered topics in the philosophy of language, perception, and metaphysics. The present volume contains revised and expanded versions of the papers presented at the workshop. (shrink)
Linguistic meaning underdetermines what is said. This has consequences for philosophical accounts of meaning, communication, and propositional attitude reports. I argue that the consequence we should endorse is that utterances typically express many propositions, that these are what speakers mean, and that the correct semantics for attitude reports will handle this fact while being relational and propositional.
In Jeffrey King’s theory of structured propositions, propositional structure mirrors the syntactic structure of natural language sentences that express it. I provide cases where this claim individuates propositions too finely across languages. Crucially, King’s paradigmatic proposition-fact ^that Dara swims^ cannot be believed by a monolingual Greek speaker, due to Greek syntax requiring an obligatory article in front of proper names. King’s two possible replies are: (i) to try to streamline the syntax of Greek and English; or (ii) to (...) insist that English speakers can believe propositions inexpressible in Greek. I argue that the former option entails giving up a neo-Russelian framework, and the latter makes King’s account arbitrary or trivial. I conclude that the mirroring claim is untenable. (shrink)
Most direct reference theorists about indexicals and proper names have adopted the thesis that singular propositions about physical objects are composed of physical objects and properties.1 There have been a number of recent proponents of such a view, including Scott Soames, Nathan Salmon, John Perry, Howard Wettstein, and David Kaplan.2 Since Kaplan is the individual who is best known for holding such a view, let's call a proposition that is composed of objects and properties a K-proposition. In this paper, (...) I will attempt to show that a direct reference view about the content of proper names and indexicals leads very naturally to the position that all singular propositions about physical objects are K-propositions.3 Then, I will attempt to show that this view of propositions is false. I will spend the bulk of the paper on this latter task. My goal in the paper, then, is to show that adopting the direct reference thesis comes at a cost problems the view has with problems such as opacity and the significance of some identity statements; it comes at even more of a cost). (shrink)
An important objection to sententialist theories of attitude reports is that they cannot accommodate the principle that one cannot know that someone believes that p without knowing what it is that he believes. This paper argues that a parallel problem arises for propositionalist accounts that has gone largely unnoticed, and that, furthermore, the usual resources for the propositionalist do not afford an adequate solution. While non-standard solutions are available for the propositionalist, it turns out that there are parallel solutions that (...) are available for the sententialist. Since the difficulties raised seem to show that the mechanism by which sentential complements serve to inform us about attitudes and about sentence meaning does not depend on their referring to propositions, this casts doubt on whether talk of propositions should retain a significant theoretical role in the enterprise of understanding thought, language and communication. (shrink)
Is the way we use propositions to individuate beliefs and other intentional states analogous to the way we use numbers to measure weights and other physical magnitudes? In an earlier paper [2], I argued that there is an important disanalogy. One and the same weight can be 'related to' different numbers under different units of measurement. Moreover, the choice of a unit of measurement is arbitrary,in the sense that which way we choose doesn't affect the weight attributed to the (...) object. But it makes little sense to say that one and the same belief can be related to different propositions: different proposition means different belief. So there is no analogous arbitrary choice. (shrink)
Reductionist realist accounts of certain entities, such as the natural numbers and propositions, have been taken to be fatally undermined by what we may call the problem of arbitrary identification. The problem is that there are multiple and equally adequate reductions of the natural numbers to sets (see Benacerraf, 1965), as well as of propositions to unstructured or structured entities (see, e.g., Bealer, 1998; King, Soames, & Speaks, 2014; Melia, 1992). This paper sets out to solve the problem (...) by canvassing what we may call the arbitrary reference strategy. The main claims of such strategy are 2. First, we do not know which objects are the referents of proposition and numerical terms since their reference is fixed arbitrarily. Second, our ignorance of which object is picked out as the referent does not entail that no object is referred to by the relevant expression. Different articulations of the strategy are assessed, and a new one is defended. (shrink)
A number of traditional roles that propositions are supposed to play are outlined. Philosophical theories of the nature of propositions are then surveyed, together with considerations for and against, with an eye on the question whether any single notion of a proposition is suited to play all or any of these roles. Approaches discussed include: (1) the structureless possible-worlds theory; (2) the structured Russellian theory; and (3) the structured Fregean theory. It is noted that it is often unclear (...) whether these are accounts of what propositions are, ontologically speaking, or whether they are accounts of how propositions are best represented in a formal semantic theory. (shrink)
Propositions have played a central role in philosophy of language since Frege. I will argue that the notion of a proposition, because of a range of philosophical problems as well as problems of linguistic adequacy, should be replaced by a different notion, for almost all the roles for it has been invoked, namely by the notion of an attitudinal object. Attitudinal objects are entities like ‘John’s belief that S’, ‘John’s claim that S’, and ‘John’s desire to do X’. Attitudinal (...) objects are closely related to, yet ontologically distinct from mental events and speech acts. (shrink)
Presentists, who believe that only present objects exist, should accept a thisness ontology, since it can do considerable work in defence of presentism. In this paper, I propose a version of presentism that involves thisnesses of past and present entities and I argue this view solves important problems facing standard versions of presentism.
Propositionalism is the view that all intentional states are propositional states, which are states with a propositional content, while objectualism is the view that at least some intentional states are objectual states, which are states with objectual contents, such as objects, properties, and kinds. This paper argues that there are two distinct ways of understanding propositionalism and objectualism: (1) as views about the deep nature of the contents of intentional states, and (2) as views about the superficial character of the (...) contents of intentional states. I argue that we should understand the views in the second way. I also argue that the propositionalism debate is fairly independent from debates over the deep nature of intentionality, and that this has implications for arguments for propositionalism and objectualism from claims about the nature of intentional content. I close with a short discussion of how related points apply to the debate over singular content. (shrink)
In nearly forty years’ of work, Simon Blackburn has done more than anyone to expand our imaginations about the aspirations for broadly projectivist/expressivist theorizing in all areas of philosophy. I know that I am far from alone in that his work has often been a source of both inspiration and provocation for my own work. It might be tempting, in a volume of critical essays such as this, to pay tribute to Blackburn’s special talent for destructive polemic, by seeking to (...) take down that by which I’ve been most provoked over the years. But Blackburn’s biting wit has both more wit and more bite than I could hope to emulate. So instead I’ll try to emulate here what I’ve admired the most about Blackburn – the constructive vein of much of his work. (shrink)
This is a paper in which I argue that problems of transworld identity and the truth in-truth at distinction are motivated by unhelpful pictures we have in mind while doing metaphysics.
The problem of truthmakers for negative propositions was introduced by Bertrand Russell in 1918. Since then the debate has mostly been concerned with whether to accept or reject their existence, and little has been said about what it is that makes a negative proposition negative. This is a problem as it is obvious that you cannot just read it off from the grammar of a sentence. The aim of this paper is to demonstrate that propositions may be negative (...) or positive in many ways: it offers a typology, and shows how the question of the existence of negative facts will receive a different answer depending on its relationship to that typology. (shrink)
According to the classical account, propositions are sui generis, abstract, intrinsically-representational entities and our cognitive attitudes, and the token states within us that realize those attitudes, represent as they do in virtue of their propositional objects. In light of a desire to explain how it could be that propositions represent, much of the recent literature on propositions has pressured various aspects of this account. In place of the classical account, revisionists have aimed to understand propositions in (...) terms of more familiar entities such as facts, types of mental or linguistic acts, and even properties. But we think that the metaphysical story about propositions is much simpler than either the classical theorist or the revisionist would have you believe. In what follows, we argue that a proper understanding of the nature of our cognitive relations to propositions shows that the question of whether propositions themselves represent is, at best, a distraction. We will argue that once this distraction is removed, the possibility of a very pleasing, minimalist story of propositions emerges; a story that appeals only to assumptions that are shared by all theorists in the relevant debate. (shrink)
Recent work in philosophy of language has raised significant problems for the traditional theory of propositions, engendering serious skepticism about its general workability. These problems are, I believe, tied to fundamental misconceptions about how the theory should be developed. The goal of this paper is to show how to develop the traditional theory in a way which solves the problems and puts this skepticism to rest. The problems fall into two groups. The first has to do with reductionism, specifically (...) attempts to reduce propositions to extensional entities-either extensional functions or sets. The second group concerns problems of fine grained content-both traditional 'Cicero'/'Tully' puzzles and recent variations on them which confront scientific essentialism. After characterizing the problems, I outline a non-reductionist approach-the algebraic approach-which avoids the problems associated with reductionism. I then go on to show how the theory can incorporate non-Platonic (as well as Platonic) modes of presentation. When these are implemented nondescriptively, they yield the sort of fine-grained distinctions which have been eluding us. The paper closes by applying the theory to a cluster of remaining puzzles, including a pair of new puzzles facing scientific essentialism. (shrink)
Language was central to Hobbes's understanding of human beings and their mental abilities, and criticism of other philosophers' uses of language became a favorite critical tool for him. This paper connects Hobbes's theories about language to his criticisms of others' language, examining Hobbes's theories of propositions and truth, and how they relate to his claims that various sorts of proposition are absurd. It considers whether Hobbes in fact means anything more by 'absurd' than 'false'. And it pays particular attention (...) to Hobbes's categorization of causes of absurdity and of types of incoherent proposition, arguing that Hobbes's approach is only loosely related to later discussions of category mistakes. (shrink)
Je défends ici la nécessité, et ébauche une première version, d’une théorie iconique des propositions. Selon celle-ci, les propositions sont comme les objets de représentation, ou similaires à eux. Les propositions, suivant cette approche, sont des propriétés que l’esprit instancie lorsqu’il modélise le monde. Je connecte cette théorie aux récents développements de la littérature académique sur les propositions, ainsi qu’à une branche de recherches en sciences cognitives, qui explique certains types de représentations mentales en termes d’iconicité. (...) I motivate the need for, and then sketch, an iconic theory of propositions according to which propositions are like or similar to their objects of representation. Propositions on this theory are properties that the mind instantiates when it models the world. I connect the theory to recent developments in the propositions literature as well as to a strain of cognitive science that explains some kinds of mental representation in terms of iconicity. (shrink)
The paper argues that philosophers commonly misidentify the substitutivity principle involved in Russell’s puzzle about substitutivity in “On Denoting”. This matters because when that principle is properly identified the puzzle becomes considerably sharper and more interesting than it is often taken to be. This article describes both the puzzle itself and Russell's solution to it, which involves resources beyond the theory of descriptions. It then explores the epistemological and metaphysical consequences of that solution. One such consequence, it argues, is that (...) Russell must abandon his commitment to propositions. (shrink)
This is the only complete logic for properties, relations, and propositions (PRPS) that has been formulated to date. First, an intensional abstraction operation is adjoined to first-order quantifier logic, Then, a new algebraic semantic method is developed. The heuristic used is not that of possible worlds but rather that of PRPS taken at face value. Unlike the possible worlds approach to intensional logic, this approach yields a logic for intentional (psychological) matters, as well as modal matters. At the close (...) of the paper, the origin of incompleteness in logic is investigated. The culprit is found to be the predication relation, a relation on properties and relations that is expressed in natural language by the copula. (shrink)
This paper offers an analysis of a hitherto neglected text on insoluble propositions dating from the late XiVth century and puts it into perspective within the context of the contemporary debate concerning semantic paradoxes. The author of the text is the italian logician Peter of Mantua (d. 1399/1400). The treatise is relevant both from a theoretical and from a historical standpoint. By appealing to a distinction between two senses in which propositions are said to be true, it offers (...) an unusual solution to the paradox, but in a traditional spirit that contrasts a number of trends prevailing in the XiVth century. It also counts as a remarkable piece of evidence for the reconstruction of the reception of English logic in italy, as it is inspired by the views of John Wyclif. Three approaches addressing the Liar paradox (Albert of Saxony, William Heytesbury and a version of strong restrictionism) are first criticised by Peter of Mantua, before he presents his own alternative solution. The latter seems to have a prima facie intuitive justification, but is in fact acceptable only on a very restricted understanding, since its generalisation is subject to the so-called revenge problem. (shrink)
Metaphysically possible worlds have many uses. Epistemically possible worlds promise to be similarly useful, especially in connection with propositions and propositional attitudes. However, I argue that there is a serious threat to the natural accounts of epistemically possible worlds, from a version of Russell’s paradox. I contrast this threat with David Kaplan’s problem for metaphysical possible world semantics: Kaplan’s problem can be straightforwardly rebutted, the problems I raise cannot. I argue that although there may be coherent accounts of epistemically (...) possible worlds with fruitful applications, any such an account must fundamentally compromise the basic idea behind epistemic possibility. (shrink)
We present two defeasible logics of norm-propositions (statements about norms) that (i) consistently allow for the possibility of normative gaps and normative conflicts, and (ii) map each premise set to a sufficiently rich consequence set. In order to meet (i), we define the logic LNP, a conflict- and gap-tolerant logic of norm-propositions capable of formalizing both normative conflicts and normative gaps within the object language. Next, we strengthen LNP within the adaptive logic framework for non-monotonic reasoning in order (...) to meet (ii). This results in the adaptive logics LNPr and LNPm, which interpret a given set of premises in such a way that normative conflicts and normative gaps are avoided ‘whenever possible’. LNPr and LNPm are equipped with a preferential semantics and a dynamic proof theory. (shrink)
There is an apparent dilemma for hierarchical accounts of propositions, raised by Bruno Whittle : either such accounts do not offer adequate treatment of connectives and quantifiers, or they eviscerate the logic. I discuss what a plausible hierarchical conception of propositions might amount to, and show that on that conception, Whittle’s dilemma is not compelling. Thus, there are good reasons why proponents of hierarchical accounts of propositions did not see the difficulty Whittle raises.
A Commonplace of recent philosophy of mind is that intentional states are relations between thinkers and propositions. This thesis-call it the 'Relational Thesis'-does not depend on any specific theory of propositions. One can hold it whether one believes that propositions are Fregean Thoughts, ordered n-tuples of objects and properties or sets of possible worlds. An assumption that all these theories of propositions share is that propositions are abstract objects, without location in space or time...
On rationalist infallibilism, a wide range of both (i) analytic and (ii) synthetic a priori propositions can be infallibly justified, i.e., justified in a way that is truth-entailing. In this paper, I examine the second thesis of rationalist infallibilism, what might be called ‘synthetic a priori infallibilism’. Exploring the seemingly only potentially plausible species of synthetic a priori infallibility, I reject the infallible justification of so-called self-justifying propositions.
"Jim would still be alive if he hadn't jumped" means that Jim's death was a consequence of his jumping. "x wouldn't be a triangle if it didn't have three sides" means that x's having a three sides is a consequence its being a triangle. Lewis takes the first sentence to mean that Jim is still alive in some alternative universe where he didn't jump, and he takes the second to mean that x is a non-triangle in every alternative universe where (...) it doesn't have three sides. Why did Lewis have such obviously wrong views? Because, like so many of his contemporaries, he failed to grasp the truth that it is the purpose of the present paper to demonstrate, to wit: No coherent doctrine assumes that statements about possible worlds are anything other than statements about the dependence-relations governing our world. The negation of this proposition has a number of obviously false consequences, for example: all true propositions are necessarily true (there is no modal difference between "2+2=4" and "Socrates was bald"); all modal terms (e.g. "possible," "necessary") are infinitely ambiguous; there is no difference between laws of nature (e.g. "metal expands when heated") and accidental generalizations (e.g. "all of the coins in my pocket are quarters"); and there is no difference between the belief that 1+1=2 and the belief that arithmetic is incomplete. Given that possible worlds are identical with mathematical models, it follows that the concept of model-theoretic entailment is useless in the way of understanding how inferences are drawn or how they should be drawn. Given that the concept of formal-entailment is equally useless in these respects, it follows that philosophers and mathematicians have simply failed to shed any light on the nature of the consequence-relation. Q's being either a formal or a model-theoretic consequence of P is parasitic on its bearing some third, still unidentified relation to P; and until this relation has been identified, the discipline of philosophical logic has yet to begin. (shrink)
Can we find propositions that cannot rationally be denied in any possible world without assuming the existence of that same proposition, and so involving ourselves in a contradiction? In other words, can we find transworld propositions needing no further foundation or justification? Basically, three differing positions can be imagined: firstly, a relativist position, according to which ultimately founded propositions are impossible; secondly, a meta-relativist position, according to which ultimately founded propositions are possible but unnecessary; and thirdly, (...) an absolute position, according to which such propositions are necessary. In this short essay I show that under the premise of modal logic S5 with constant domain there are ultimately founded propositions and that their existence is even necessary, and I will give some reasons for the superiority of S5 over other logics. (shrink)
Higher-order theories of properties, relations, and propositions are known to be essentially incomplete relative to their standard notions of validity. It turns out that the first-order theory of PRPs that results when first-order logic is supplemented with a generalized intensional abstraction operation is complete. The construction involves the development of an intensional algebraic semantic method that does not appeal to possible worlds, but rather takes PRPs as primitive entities. This allows for a satisfactory treatment of both the modalities and (...) the propositional attitudes, and it suggests a general strategy for developing a comprehensive treatment of intensional logic. (shrink)
This paper discusses the reports in Diogenes Laertius and in Sextus Empiricus concerning the classification of propositions. It is argued that the material in Sextus uses a source going back to the Dialectical school whose most prominent members were Diodorus Cronus and Philo of Megara. The material preserved in Diogenes Laertius, on the other hand, goes back to Chrysippus.
This paper corrects a mistake I saw students make but I have yet to see in print. The mistake is thinking that logically equivalent propositions have the same counterexamples—always. Of course, it is often the case that logically equivalent propositions have the same counterexamples: “every number that is prime is odd” has the same counterexamples as “every number that is not odd is not prime”. The set of numbers satisfying “prime but not odd” is the same as the (...) set of numbers satisfying “not odd but not not-prime”. The mistake is thinking that every two logically-equivalent false universal propositions have the same counterexamples. Only false universal propositions have counterexamples. A counterexample for “every two logically-equivalent false universal propositions have the same counterexamples” is two logically-equivalent false universal propositions not having the same counterexamples. The following counterexample arose naturally in my sophomore deductive logic course in a discussion of inner and outer converses. “Every even number precedes every odd number” is counterexemplified only by even numbers, whereas its equivalent “Every odd number is preceded by every even number” is counterexemplified only by odd numbers. Please let me know if you see this mistake in print. Also let me know if you have seen these points discussed before. I learned them in my own course: talk about learning by teaching! (shrink)
I argue that George Nakhnikian's analysis of the logic of cogito propositions (roughly, Descartes's 'cogito' and 'sum') is incomplete. The incompleteness is rectified by showing that disjunctions of cogito propositions with contingent, non-cogito propositions satisfy conditions of incorrigibility, self-certifyingness, and pragmatic consistency; hence, they belong to the class of propositions with whose help a complete characterization of cogito propositions is made possible.
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