Based on her earlier ground-breaking axiomatization of quantified modal logic, the papers collected here by the distinguished philosopher Ruth Barcan Marcus cover much ground in the development of her thought, spanning from 1961 to 1990. The first essay here introduces themes initially viewed as iconoclastic, such as the necessity of identity, the directly referential role of proper names as "tags", the Barcan Formula about the interplay of possibility and existence, and alternative interpretations of quantification. Marcus also addresses the (...) putative puzzles about substitutivity and about essentialism. The collection also includes influential essays on moral conflict, on belief and rationality, and on some historical figures. Many of her views have been incorporated into current theories, while others remain part of a continuing debate. (shrink)

The Barcan formula (BF) is commonly paraphrased as the schematic conditional that if it is possible that there be a phi then something or other is possibly a phi. It is validated by the most straightforward systems of quantified modal logic. It is also widely considered to pose a threat to the commonsensical metaphysical view that there are no non-actual (or ‘merely possible’) things. I show how BF can be cleared of such a charge by construing it as a (...) bridge principle connecting modality de dicto and modality de re while retaining a Russellian robust sense of reality in modal matters. (shrink)

The paper criticizes the truthmaker principle that every truth is made true by something. If we interpret ‘something’ as quantifying into sentence position, we can interpret the principle as a harmless logical truth, but that is not what advocates of the principle intend. They interpret ‘something’ as quantifying into name position, and the principle as requiring the existence of truthmaking individuals. The paper argues that we have no reason to believe the principle on this interpretation. Moreover, the converse Barcan (...) formula is inconsistent with the existence of truthmaking individuals for contingent truths. Considerations about our ability to count possible truthmaking individuals are used to argue that we should prefer the converse Barcan formula. (shrink)

It has been argued by Bernard Linsky and Edward Zalta, and independently by Timothy Williamson, that the best quantified modal logic is one that validates both the Barcan Formula and its converse. This requires that domains be fixed across all possible worlds. All objects exist necessarily; some – those we would usually consider contingent – are concrete at some worlds and non-concrete (but still existent) at others. Linsky and Zalta refer to such objects as ‘contingently non-concrete’. I defend the (...) standard usage of the word ‘exists’, and the view that many objects exist only contingently. I argue that the Linsky/Zalta analysis, and to a lesser extent Williamson’s, suffers not only from a peculiar ontology but also from two related formal difficulties. Their analysis gives either counter-intuitive or ad hoc results about essences, and it fails to accommodate contingently existing abstracta. (shrink)

This paper presents structural similarities and historical connections between Prior’s rejection of the Barcan formula and his critique of Berkeley’s master argument for idealism in his 1955 paper “Berkeley in Logical Form”. Making use of Mackie’s paper “Self-Refutation—A Formal Analysis”, it concludes with some suggestions concerning what is at stake in the debate between Prior and Berkeley and in structurally similar debates such as whether to accept the Barcan formula.

A (normal) system of propositional modal logic is said to be complete iff it is characterized by a class of (Kripke) frames. When we move to modal predicate logic the question of completeness can again be raised. It is not hard to prove that if a predicate modal logic is complete then it is characterized by the class of all frames for the propositional logic on which it is based. Nor is it hard to prove that if a propositional modal (...) logic is incomplete then so is the predicate logic based on it. But the interesting question is whether a complete propositional modal logic can have an incomplete extension. In 1967 Kripke announced the incompleteness of a predicate extension of S4. The purpose of the present article is to present several such systems. In the first group it is the systems with the Barcan Formula which are incomplete, while those without are complete. In the second group it is those without the Barcan formula which are incomplete, while those with the Barcan Formula are complete. But all these are based on propositional systems which are characterized by frames satisfying in each case a single first-order sentence. (shrink)

info:eu-repo/semantics/publishedVersion.

We present in this note a plea for Barcan formula. This view connects Barcan formula with a modal principle that expresses the -Introduction rule of first-order logic.

On its usual interpretation, the Barcan Formula—◊∃_xB_ → ∃_x_◊_B_—says that, if there could have been something that is such and such a way, then there is something that could have been that way. It is traditionally held that contingentist actualists should—indeed, must—reject the Barcan Formula. I argue that contingentist actualists should—indeed, must—endorse the Barcan Formula, at least assuming a standard, Tarskian conception of truth and truth preservation. I end by proposing a logic for contingentist actualists that validates (...) the Barcan Formula. This logic has the surprising feature of also validating the Converse Barcan Formula, □∀_xB_ → ∀_x_□_B_, while still invalidating related formulas—such as □∀_x_□∃_y x_ = _y_ (NNE)—that contingentist actualists should reject. It does this by employing models with fixed domains but assignments to the identity predicate that vary across worlds. (shrink)

The revolution in semantics in the late 1960s and 1970s overturned an earlier competing paradigm, ‘translational’ semantics. I revive and defend Prior’s translational semantics for modals and tense-modals. I also show how to extend Prior’s propositional modal semantics to quantificational modal logic, and use the resulting semantics to formalize Prior’s own counterexample to the Barcan Formula.

The paper is intended to provide a full-scale defence of the infamous Barcan Formulae. Not only do I put forth some arguments, both semantic and metaphysical, against recent criticism; I also take pains at supplying some rationale in favour of the formal semantics underlying the Formulae, namely Possibilist quantification. Such a task is carried out through an argument for Compositional Nihilism, according to which nothing but mereological simples ever exists, and consequently through an informal sketch of the (...) metaphysics of possible worlds grounded upon Compositional Nihilism. The paper closes by surveying the main reasons why the account championed here isn’t defective with respect to other possibilist accounts of existence and modality presently on stage. (shrink)

The Barcan formula is a theorem of quantified modal logic. Its most straightforward interpretation appears to commit one to “possibilism,” the view that merely possible things exist. Alternative systems of logic revise the formal semantics to preclude the theorem and its consequences. The crux, however, is the modal metaphysics presupposed by the formal semantics. This paper presents an alternative metaphysics of possibility that follows Augustine’s suggestion that God’s plan is only one of a range of alternative histories for a (...) creation. The metaphysics is a version of “trace actualism”—neither pure possibilism nor pure actualism. (shrink)

En esta nota discutimos una forma generaldel Teorema de Deducción (TD) para sistemas modales de primer orden, la cual permite derivar varias otras formulaciones del mismoque aparecen en la literatura, así como su relación con la Fórmula de Barcan.

Se ha destacado recientemente que la Fórmula de Barcan y la Conversa de la Fórmula de Barcan para lógica modal cuantificacional de orden superior parecen válidas. Si se interpreta que los cuantificadores tienen como rango propiedades, la validez de y de orden superior parece implicar la existencia de universales trascendentes, esto es, universales que no requieren estar instanciados para existir en un mundo posible. Este trabajo discute esta línea de argumentación. En primer lugar, se sostiene que la semántica (...) en la que los resultados de validez se siguen no requiere que las ‘intensiones’ asignadas a las variables de orden superior estén instanciadas en un mundo posible para que la intensión exista ahí. El defensor de universales inmanentes objetaría esta suposición. En una semántica modificada, más neutral, y de orden superior ya no son válidas. En segundo lugar, se sostiene que, incluso si se concediese la validez de y de orden superior, no se obtendrían resultados metafísicos sustantivos, pues diferentes formas de nominalismo y diferentes teorías de tropos no tendrían dificultades en aceptar y de orden superior. (shrink)

RESUMEN Se ha destacado que la Fórmula de Barcan -FB- y la Conversa de la Fórmula de Barcan -CFB- para lógica modal cuantificacional de orden superior parecen válidas. Si se interpreta que los cuantificadores tienen como rango propiedades, la validez de FB y CFB parece implicar la existencia de universales trascendentes, que no requieren estar instanciados para existir en un mundo posible. Se discute esta argumentación, porque la semántica, en la que los resultados de validez se siguen, no (...) requiere que las ‘intensiones' asignadas a las variables de orden superior estén instanciadas en un mundo posible para que la intensión exista ahí. En una semántica modificada, más neutral, FB y CFB de orden superior ya no son válidas. Además se sostiene que, incluso si FB y CFB de orden superior fuesen válidas, no se obtendrían resultados metafísicos sustantivos, pues diferentes formas de nominalismo y teorías de tropos las aceptarían. ABSTRACT It has been pointed out that the Barcan Formula -BF- and the Converse Barcan Formula -CBF- seem to be valid for higher-order modal quantificational logic. If quantifiers are construed as ranging over properties, the validity of BF and CBF seems to entail the existence of transcendent universals that do not require instantiation in order to exist in a possible world. The paper discusses this argument given that semantics, in which validity results follow from one another, do not require that the "intensions" assigned to higher- order variables be instantiated in a possible world in order for the intension to exist in such a world. In a modified, more neutral semantics, higher-order BF and CBF are no longer valid. The paper also argues that even if higher-order BF and CBF were valid, no substantive metaphysical results would be obtained, since different forms of nominalism and theories of tropes would accept them. (shrink)

The great contribution Marcus has made to several of intensely discussed topics in philosophy might not have been noticed fully without this collection of some of her most important articles that makes it evident that her achievement is not limited to inventing the famous Barcan formula.

In 2003 Zia Movahed pointed to a passage of Avicenna, written probably in 1022, which Movahed claimed anticipated the modal formula of Barcan (that ‘For every |$x$| necessarily |$\phi $|’ entails ‘Necessarily for every |$x$||$\phi $|’), and its converse. Since 2003, examination of early logical writings of Avicenna has clarified how he understood entailments between modal sentences, using his own new temporal language to provide a kind of semantics. In the light of that, Movahed’s claim for the Barcan (...) formula needs some tidying up but is basically correct. But by his semantics Avicenna should not have claimed the converse Barcan formula and probably didn’t claim it. (shrink)

Obituary. Ruth Barcan Marcus' contributions to modal logic and to semantics are discussed.

The paper presents a semantics for quantified modal logic which has a weaker axiomatization than the usual Kripke semantics. In particular, the Barcan Formula and its converse are not valid with the proposed semantics. Subclasses of models which validate BF and other interesting formulas are presented. A completeness theorem is proved, and the relation between this result and completeness with respect to Kripke models is investigated.

Based on her earlier ground-breaking axiomatization of quantified modal logic, the papers collected here by the distinguished philosopher Ruth Barcan Marcus cover much ground in the development of her thought, including influential essays on moral conflict, on belief and rationality, and on some historical figures.

History and Philosophy of Logic, Volume 32, Issue 2, Page 103-106, May 2011.

In this paper ontological implications of the Barcan formula and its converse will be discussed at the conceptual and technical level. The thesis that will be defended is that sentential moods are not ontologically neutral since the rejection of ontological implications of Barcan formula and its converse is a condition of a possibility of the imperative mood. The paper is divided into four sections. In the first section a systematization of semantical systems of quantified modal logic is introduced (...) for the purpose of making explicit their ontological presuppositions. In this context Jadacki's ontological difference between being and existence is discussed and analyzed within the framework of hereby proposed system of quantified modal logic. The second section discusses ontological implications of the Barcan formula and its converse within the system accommodating the difference between being and existence. The third section presents a proof of incompatibility of the Barcan formula and its converse with the use of imperatives. In the concluding section, a thesis on logical pragmatics foreclosing the dilemma between necessitism and contingentism is put forward and defended against some objections. (shrink)

Marcus argues that moral dilemmas are real, but that they are not the result of inconsistent moral principles. Moral principles are consistent just in case there is some world where all principles are 'obeyable.' They are inconsistent just in case there is no world where all are 'obeyable.' What this logical point is meant to show is that moral dilemmas do not make moral codes inconsistent. She also discusses guilt, and argues that guilt is still appropriate even in cases of (...) conflict, even when the agent thinks the right thing to do is clear. (shrink)

In "An Alternative Semantics for Quantified Relevant Logic" (JSL 71 (2006)) we developed a semantics for quantified relevant logic that uses general frames. In this paper, we adapt that model theory to treat quantified modal logics, giving a complete semantics to the quantified extensions, both with and without the Barcan formula, of every proposi- tional modal logic S. If S is canonical our models are based on propositional frames that validate S. We employ frames in which not every set (...) of worlds is an admissible proposition, and an alternative interpretation of the uni- versal quantifier using greatest lower bounds in the lattice of admissible propositions. Our models have a fixed domain of individuals, even in the absence of the Barcan formula. For systems with the Barcan formula it is possible to preserve the usual Tarskian reading of the quantifier, at the expensive of sometimes losing va- lidity of S in the underlying propositional frames. We apply our results to a number of logics, including S4.2, S4M and KW, whose quantified extensions are incomplete for the standard semantics. (shrink)

Alternative readings of quantification are considered. The absence of an unequivocal translation into ordinary speech is noted. Some examples are cited which, in the opinion of the author, are a result of equivocal readings of quantification, or unnecessarily restrictive readings which obscure its primary function.