Disjunctive antecedent conditionals —conditionals of the form if A or B, C—sometimes seem to entail both of their simplifications and sometimes seem not to. I argue that this behavior reveals a genuine ambiguity in DACs. Along the way, I discuss a new observation about the role of focal stress in distinguishing the two interpretations of DACs. I propose a new theory, according to which the surface form of a DAC underdetermines its logical form: on one possible logical form, if A (...) or B, C does entail both of its simplifications, while on the other, it does not. (shrink)

Gonzalo Rodriguez-Pereyra (2006) argues against attempts to preserve the entailment principle (or a restriction of it) while avoiding the explosion of truthmakers for necessities and truthmaker triviality. In doing so, he both defends the disjunction thesis--if something makes true a disjunctive truth, then it makes true one of its disjuncts--, and rejects the conjunction thesis--if something makes tue a conjunctive truth, then it makes true each of its conjuncts. In my discussion, I provide plausible counterexamples to the disjunction (...) thesis, and contend that Rodriguez-Pereyra's general defence of it fails. Then I defend the conjunction thesis from Rodriguez-Pereyra's case against it. (shrink)

This paper defends the case against (sparse) disjunctive properties by means of four Armstrongian arguments. The first of these is a logical atomist argument from truthmaking, which is, broadly speaking, ‘Armstrongian’ (Armstrong 1997). This argument is strong – although it stands or falls with the relevant notion of truthmaking, as it were. However, three arguments, which are prima facie independent of truthmaking, can be found explicitly early in Armstrong’s middle period. Two of these early arguments face a serious objection put (...) forward forcefully by Louise Antony (2003) and Alan Penczek (1997), respectively. I consider these objections and argue that they fail. Thus, even if the argument from truthmaking is indecisive, disjunctive properties should be rejected. (shrink)

Perception can’t have disjunctive content. Whereas you can think that a box is blue or red, you can’t see a box as being blue or red. Based on this fact, I develop a new problem for the ambitious predictive processing theory, on which the brain is a machine for minimizing prediction error, which approximately implements Bayesian inference. I describe a simple case of updating a disjunctive belief given perceptual experience of one of the disjuncts, in which Bayesian inference and predictive (...) coding pull in opposite directions, with the former implying that one’s confidence in the belief should increase, and the latter implying that it should decrease. Thus, predictive coding fails to approximately implement Bayesian inference across the interface between belief and perception. (shrink)

The disjunction problem and the distality problem each presents a challenge that any theory of mental content must address. Here we consider their bearing on purely probabilistic causal theories. In addition to considering these problems separately, we consider a third challenge—that a theory must solve both. We call this “the hard problem.” We consider 8 basic ppc theories along with 240 hybrids of them, and show that some can handle the disjunction problem and some can handle the distality (...) problem, but none can handle the hard problem. This is our main result. We then discuss three possible responses to that result, and argue that though the first two fail, the third has some promise. (shrink)

Perceptual experiences are often divided into the following three broad categories: veridical perceptions, illusions, and hallucinations. For example, when one has a visual experience as of a red object, it may be that one is really seeing an object and its red colour (veridical perception), that one is seeing a green object (illusion), or that one is not seeing an object at all (hallucination). Many maintain that the same account should be given of the nature of the conscious experience that (...) occurs in each of these three cases. Those who hold a disjunctive theory of perception deny this. Disjunctivists typically reject the claim that the same kind of experience is common to all three cases because they hold views about the nature of veridical perception that are inconsistent with it. (shrink)

There is an initial presumption against disjunctive causes. First of all, for some people causation is a relation between events. But, arguably, there are no disjunctive events, since events are particulars and thus they have spatiotemporal locations, while it is unclear what the spatiotemporal location of a disjunctive event could be.1 More importantly, even if one believes that entities like facts can enter in causal relations, and even if there are disjunctive facts, it is still hard to see how disjunctive (...) facts could be causes. Imagine, for instance, the following scenario. I have a gun filled with red paint and another gun filled with blue paint, and I fire both guns at my neighbor’s white wall. A moment later, there is a graffiti on the wall and my neighbor notifies the police. He would have done so regardless of the graffiti’s color, since all he cares about is the existence of a graffiti on his wall. Is it plausible to claim that a disjunctive fact is a cause of his notifying the police? In particular, is it plausible to claim that he notified the police because I fired the red-paint gun or the blue-paint gun (the thought being that my firing paint of either color would have sufficed)? It seems not. The police was notified because of the actual graffiti on the wall, and the actual graffiti on the wall is made of a certain pattern of colored patches. Imagine, that, as it turns out, there are patches of both colors on the wall. Then it seems that both my firing the red-paint gun and my firing the blue-paint gun were causes of my neighbor’s notifying the police. In other words, my firing the red-paint gun and my firing the blue-paint gun jointly caused the outcome: each of them was a contributory cause of the outcome’s occurrence. On the other hand, imagine that there are only patches of one color on the wall. Then it seems that my firing only one of the guns was a cause. Either way, the disjunction fails to be a cause: either my firing the red-paint gun was a cause, or my firing the blue-paint gun was a cause, or they were both causes, but their disjunction was not.. (shrink)

The relation between ex falso and disjunctive syllogism, or even the justification of ex falso based on disjunctive syllogism, is an old topic in the history of logic. This old topic reappears in contemporary logic since the introduction of minimal logic by Johansson. The disjunctive syllogism seems to be part of our general non-problematic inferential practices and superficially it does not seem to be related to or to depend on our acceptance of the frequently disputable ex falso rule. We know (...) that the acceptance of the ex falso is a sufficient condition for the acceptance of the disjunctive syllogism, but the interesting question is: is the ex falso a necessary condition for the acceptance of the disjunctive syllogism? The aim of the present paper is to discuss some possible ways to define systems that combines the preservation of the disjunctive syllogism with the rejection of the ex falso. (shrink)

John McDowell's conception of perceptual knowledge commits him to the claim that if I perceive that P then I am in a position to know that I perceive that P. In the first part of this essay, I present some reasons to be suspicious of this claim - reasons which derive from a general argument against 'luminosity' - and suggest that McDowell can reject this claim, while holding on to almost all of the rest of his conception of perceptual knowledge, (...) by supplementing his existing disjunctive conception of experience with a new disjunctive conception of perceiving. In the second part of the essay, I present some reasons for thinking that one's justification, in cases of perceptual knowledge, consists not in the fact that one perceives that P but in the fact that one perceives such-and-such. I end by suggesting that the disjunctive conception of perceiving should be understood as a disjunctive conception of perceiving such-and-such. (shrink)

Many philosophers have been attracted to the idea of using the logical form of a true sentence as a guide to the metaphysical grounds of the fact stated by that sentence. This paper looks at a particular instance of that idea: the widely accepted principle that disjunctions are grounded in their true disjuncts. I will argue that an unrestricted version of this principle has several problematic consequences and that it’s not obvious how the principle might be restricted in order to (...) avoid them. My suggestion is that, instead of trying to restrict the principle, we should distinguish between metaphysical and conceptual grounds and take the principle to apply exclusively to the latter. This suggestion, if correct, carries over to other prominent attempts at using logical form as a guide to ground. (shrink)

Classical first-order logic \ is commonly used to study logical connections between statements, that is sentences that in every context have an associated truth-value. Inquisitive first-order logic \ is a conservative extension of \ which captures not only connections between statements, but also between questions. In this paper we prove the disjunction and existence properties for \ relative to inquisitive disjunction Open image in new window and inquisitive existential quantifier \. Moreover we extend these results to several families (...) of theories, among which the one in the language of \. To this end, we initiate a model-theoretic approach to the study of \. In particular, we develop a toolkit of basic constructions in order to transform and combine models of \. (shrink)

Classical first-order logic \ is commonly used to study logical connections between statements, that is sentences that in every context have an associated truth-value. Inquisitive first-order logic \ is a conservative extension of \ which captures not only connections between statements, but also between questions. In this paper we prove the disjunction and existence properties for \ relative to inquisitive disjunction Open image in new window and inquisitive existential quantifier \. Moreover we extend these results to several families (...) of theories, among which the one in the language of \. To this end, we initiate a model-theoretic approach to the study of \. In particular, we develop a toolkit of basic constructions in order to transform and combine models of \. (shrink)

A comparison of disjunctive theories of action and perception. The development of a theory of action that warrants the name, a disjunctive theory. On this theory, there is an exclusive disjunction: either an action or an event (in one sense). It follows that in that sense basic actions do not have events intrinsic to them.

We consider the problem of moral disjunction in professional and business activities from a virtue-ethical perspective. Moral disjunction arises when the behavioral demands of a role conflict with personal morality; it is an important problem because most people in modern societies occupy several complex roles that can cause this clash to occur. We argue that moral disjunction, and the psychological mechanisms that people use to cope with it, are problematic because they make it hard to pursue virtue (...) and to live with integrity. We present role coadunation as a process with epistemic and behavioral aspects that people can use to resolve moral disjunction with integrity. When role coadunation is successful, it enables people to live virtuous lives of appropriate narrative disunity and to honor their identity-conferring commitments. We show how role coadunation can be facilitated by interpretive communities and discuss the emergence and ideal features of those communities. (shrink)

Starting from a recent paper by S. Kaufmann, we introduce a notion of conjunction of two conditional events and then we analyze it in the setting of coherence. We give a representation of the conjoined conditional and we show that this new object is a conditional random quantity, whose set of possible values normally contains the probabilities assessed for the two conditional events. We examine some cases of logical dependencies, where the conjunction is a conditional event; moreover, we give the (...) lower and upper bounds on the conjunction. We also examine an apparent paradox concerning stochastic independence which can actually be explained in terms of uncorrelation. We briefly introduce the notions of disjunction and iterated conditioning and we show that the usual probabilistic properties still hold. (shrink)

In contrast to Hintikka’s enormously complex distributive normal forms of first- order logic, this paper shows how to generate minimized disjunctive normal forms of first-order logic. An effective algorithm for this purpose is outlined, and the benefits of using minimized disjunctive normal forms to explain the truth conditions of propo- sitions expressible within pure first-order logic are presented.

This paper proves that the disjunction property, the numerical existence property, Church’s rule, and several other metamathematical properties hold true for Constructive Zermelo-Fraenkel Set Theory, CZF, and also for the theory CZF augmented by the Regular Extension Axiom.As regards the proof technique, it features a self-validating semantics for CZF that combines realizability for extensional set theory and truth.

Fine (2017a) sets out a theory of content based on truthmaker semantics which distinguishes two kinds of consequence between contents. There is entailment, corresponding to the relationship between disjunct and disjunction, and there is containment, corresponding to the relationship between conjunctions and their conjuncts. Fine associates these with two notions of parthood: disjunctive and conjunctive. Conjunctive parthood is a very useful notion, allowing us to analyse partial content and partial truth. In this chapter, I extend the notion of disjunctive (...) parthood in terms of a structural relation of refinement, which stands to disjunctive parthood much as mereological parthood stands to conjunctive parthood. Philosophically, this relation may be modelled on the determinable- determinate relation, or on a fact-to-fact notion of grounding. I discuss its connection to two other Finean notions: vagueness (understood via precisification) and arbitrary objects. I then investigate what a logic of truthmaking with refinement might look like. I argue that (i) parthood naturally gives rise to a relevant conditional; (ii) refinement underlies a relevant notion of disjunction; and so (iii) truthmaker semantics with refinement is a natural home for relevant logic. The resulting formal models draw on Fine’s (1974) semantics for relevant logics. Finally, I use this understanding of relevant semantics to investigate the status of the mingle axiom. (shrink)

The disjunction problem and the distality problem each presents a challenge that any theory of mental content must address. Here we consider their bearing on purely probabilistic causal theories. In addition to considering these problems separately, we consider a third challenge—that a theory must solve both. We call this “the hard problem.” We consider 8 basic ppc theories along with 240 hybrids of them, and show that some can handle the disjunction problem and some can handle the distality (...) problem, but none can handle the hard problem. This is our main result. We then discuss three possible responses to that result, and argue that though the first two fail, the third has some promise. (shrink)

In this paper I deal with the relation between the disjunction thesis—that the truthmaking relation is distributed over a disjunction—and the necessary connection thesis—that the existence of some entities requires the existence of other distinct entities. I will first show that because of this very relation, the arguments for and against the disjunction thesis that overlook its metaphysical considerations will fail. Finally, I will show that the commitment produced by truthmaker maximalism to totality states of affairs, or (...) some relevantly similar things, requires one to accept a necessary connection that disaffirms the disjunction thesis. (shrink)

This paper is a response to replies by Dan López de Sa and Mark Jago to my ‘Truthmaking, Entailment, and the Conjuction Thesis’. In that paper, my main aim was to argue against the Entailment Principle by arguing against the Conjunction Thesis, which is entailed by the Entailment Principle. In the course of so doing, although not essential for my project in that paper, I defended the Disjunction Thesis. López de Sa has objected both to my defence of the (...) Disjunction Thesis and my case against the Conjunction Thesis. I shall show that his objections are unfounded and based on serious misunderstandings of my position, what the relevant debate is, and some fundamental notions of Truthmaker Theory. Jago argues that accepting the Disjunction Thesis and rejecting the Conjunction Thesis is hard to maintain. But I show that Jago has not shown that accepting the Disjunction Thesis while rejecting the Conjunction Thesis is impossible or even hard to maintain. Jago believes that, to accept the Disjunction Thesis while rejecting the Conjunction Thesis, one needs to reject his axiom (T3), which says that all the truthmakers for <P&P> are truthmakers for <P>. I argue that there are reasons to reject such a principle, and the version of it that says that what makes <P&P> true makes <P> true. (shrink)

Philosophers have had difficulty in explaining the difference between disjunctive and non-disjunctive predicates. Purely syntactical criteria are ineffective, and mention of resemblance begs the question. I draw the distinction by reference to relations between borderline cases. The crucial point about the disjoint predicate 'red or green', for example, is that no borderline case of 'red' is a borderline case of 'green'. Other varieties of disjunctive predicates are: inclusively disjunctive (such as 'red or hard'), disconnected (such as 'grue' on the usual (...) definitions), and skew (such as 'grue' on an emended definition). 'Green' is not a disjunctive predicate. Nelson Goodman's new riddle of induction elicits yet another response. (shrink)

This paper investigates propositional hyperintensionality in counterfactuals. It starts with a scenario describing two children playing on a seesaw and studies the truth-value predictions for counterfactuals by four different semantic theories. The theories in question are Kit Fine’s truthmaker semantics, Luis Alonso-Ovalle’s alternative semantics, inquisitive semantics and Paolo Santorio’s syntactic truthmaker semantics. These predictions suggest that the theories that distinguish more of a given set of intensionally equivalent sentences (Fine and Alonso-Ovalle’s) fare better than those that do not (inquisitive semantics (...) and Santorio’s). Then we investigate how inquisitive semantics and Santorio can respond to these results. They can respond to them by helping themselves to considerations from Hurford disjunctions, disjunctions whose disjuncts stand in an entailment relation to one another. I argue that considerations from Hurford disjunctions are ad hoc modifications merely to predict the expected results. I conclude that the scenarios suggest a need for more fine-grained theories of sentential meaning in general. (shrink)

A pigeon has been conditioned to peck at red objects and has also been conditioned to peck at triangular objects. The pigeon is now presented with a red triangle and pecks. In virtue of which of the object's properties did the pigeon peck? I argue that the disjunctive property "red or triangular" best answers this question and that this in turn gives us reason to admit such disjunctive properties to our ontology. I also show how the criterion for causal efficacy (...) that I employ, expressed in terms of counterfactual conditionals, works to preclude spurious disjunctive properties from counting as efficacious. (shrink)

Two different kinds of multiple-conclusion consequence relations taken from Shoesmith and Smiley and Galatos and Tsinakis or Nowak, called here disjunctive and conjunctive, respectively, defined on a formal language, are considered. They are transferred into a bounded lattice and a complete lattice, respectively. The properties of such abstract consequence relations are presented.

In this paper we discuss the extent to which conjunction and disjunction can be rightfully regarded as such, in the context of infectious logics. Infectious logics are peculiar many-valued logics whose underlying algebra has an absorbing or infectious element, which is assigned to a compound formula whenever it is assigned to one of its components. To discuss these matters, we review the philosophical motivations for infectious logics due to Bochvar, Halldén, Fitting, Ferguson and Beall, noticing that none of them (...) discusses our main question. This is why we finally turn to the analysis of the truth-conditions for conjunction and disjunction in infectious logics, employing the framework of plurivalent logics, as discussed by Priest. In doing so, we arrive at the interesting conclusion that —in the context of infectious logics— conjunction is conjunction, whereas disjunction is not disjunction. (shrink)

We argue in favor of merely disjunctive effects, namely cases in which an event or fact, C, is not a cause of an effect, E1, and is also not a cause of a distinct effect, E2, and yet C is a cause of the disjunctive effect (E1 orE2). Disjunctive effects let us retain the additivity and the distributivity of causation. According to additivity, if C is a cause of E1 and C is a cause of E2, then C is a (...) cause of E1 and E2. According to distributivity, if C is a cause of E1 and E2, then C is a cause of E1 and C is a cause of E2. We draw an analogy between causation and intensional notions like believing, wanting, and owing, which also admit of merely disjunctive cases. We argue that both the Lewisian counterfactual account of causation (including its recent emendation by Sartorio) and the contrastive account of causation fail to properly account for this phenomenon. (shrink)

We introduce a tool for analysing models of $\text {CT}^-$, the compositional truth theory over Peano Arithmetic. We present a new proof of Lachlan’s theorem that the arithmetical part of models of $\text {CT}^-$ are recursively saturated. We also use this tool to provide a new proof of theorem from [8] that all models of $\text {CT}^-$ carry a partial inductive truth predicate. Finally, we construct a partial truth predicate defined for a set of formulae whose syntactic depth forms a (...) nonstandard cut which cannot be extended to a full truth predicate satisfying $\text {CT}^-$. (shrink)

This paper suggests that art cannot be defined in terms of individually necessary and jointly sufficient conditions. Instead, we propose that there are several sufficient conditions for something's being art, and that a successful definition will consist of a disjunction of minimally sufficient conditions. Our proposal owes much to the insights of Berys Gaut's ‘“Art” as a Cluster Concept’ but offers a much simpler logical formulation, which, in addition, is immune to the objections that have been raised to Gaut's (...) account. This paper agrees with Gaut's claim that there are borderline cases of art, and suggests that they arise from indeterminacy about the content of some of the minimally sufficient conditions. It is argued that this disjunctive account is superior to classical theories, resemblance-to-paradigm theories, and prototype theories of art. (shrink)

By a well-known result of Kotlarski et al., first-order Peano arithmetic \ can be conservatively extended to the theory \ of a truth predicate satisfying compositional axioms, i.e., axioms stating that the truth predicate is correct on atomic formulae and commutes with all the propositional connectives and quantifiers. This result motivates the general question of determining natural axioms concerning the truth predicate that can be added to \ while maintaining conservativity over \. Our main result shows that conservativity fails even (...) for the extension of \ obtained by the seemingly weak axiom of disjunctive correctness \ that asserts that the truth predicate commutes with disjunctions of arbitrary finite size. In particular, \ implies \\). Our main result states that the theory \ coincides with the theory \ obtained by adding \-induction in the language with the truth predicate. This result strengthens earlier work by Kotlarski and Cieśliński. For our proof we develop a new general form of Visser’s theorem on non-existence of infinite descending chains of truth definitions and prove it by reduction to Gödel’s second incompleteness theorem, rather than by using the Visser–Yablo paradox, as in Visser’s original proof. (shrink)

Reflection on skeptical scenarios in the philosophy of perception, made vivid in the arguments from illusion and hallucination, have led to the formulation of theories of the metaphysical and epistemological nature of perceptual experience. In recent times, the locus of the debate concerning the nature of perceptual experience has been the dispute between disjunctivists and common-kind theorists. Disjunctivists have held that there are substantial dissimilarities (either metaphysical or epistemological or both) between veridical perceptual experiences occurring when one perceives and perceptual (...) experiences involved in hallucination. Common-kind theorists have denied this. In this paper, I examine the nature of introspection – a faculty that has often been compared and contrasted to perception. I reflect on cases where introspection goes wrong in ways analogous to that in which our perceptual faculties can go wrong and formulate, what I take to be, an attractive theory of introspection. The cases that I focus on in which things go wrong are the case of zombies and the case of subjects with Anton’s syndrome. (Anton’s syndrome is a condition in which people who are blind claim that they can see.) I suggest that, just as it is possible to be a disjunctivist about perception, it is possible to be a disjunctivist about introspection. I argue that this is a good view of one type of introspection, namely, introspection of states that have phenomenal character, such as perceptual experiences. It has a good account to give of the cases in which such introspection seems to go wrong and it yields a plausible metaphysical and epistemological view of the nature of introspection. However, while I favour a disjunctive view of introspection, I do not favour a disjunctive view of perception. And, I suspect, that many disjunctivists about perception would not wish to condone my disjunctivist theory of introspection. I therefore go on to examine to what extent.. (shrink)

In this dissertation, I argue that all extant theories of prudential value are either a) enumeratively deficient, in that they are unable to accommodate everything that, intuitively, is a basic constituent of prudential value, b) explanatorily deficient, in that they are at least sometimes unable to offer a plausible story about what makes a given thing prudentially valuable, or c) both. In response to the unsatisfactory state of the literature, I present my own account, the Disjunctive Hybrid Theory or DHT. (...) DHT answers to and remedies each of the above inadequacies in a way that no other approach can. This account has the following general structure:Disjunctive Hybrid Theory (DHT): Thing x is basically good for person P if and only if x is either a) cared about (sufficiently and in the right way) by P, b) a bearer of (the right kind of) attitude-independent value, or c) both.Although it follows other recent accounts in combining elements from objective and subjective theories, DHT is a hybrid theory of a quite new kind. This is because it denies both subjective necessity (the constraint that, if thing x is to be basically good for person P, P must have some pro-attitude toward x) and objective necessity (the constraint that, if thing x is to be basically good for person P, x must have some attitude-independent value). I argue that the rejection of both necessity claims is called for if we are to move beyond the enumerative and explanatory limitations of existing accounts.I begin by outlining the general structure of DHT. I then argue, against various recent authors, that desire-satisfactionism remains the most appealing subjectivist approach to prudential value, in that it is best able to capture the central subjectivist insight. This insight is that a person can confer prudential value upon things by caring about them (sufficiently and in the right way). The subjectivist strand of DHT will thus be a version of desire-satisfactionism, which must be interpreted in line with what I call the object, as opposed to the combo, view. I move on to further motivate and develop the second, objectivist strand of DHT. This part of the theory involves a commitment to robustly attitude-independent prudential goods. I close by addressing some puzzles for the theory, and considering some of its more specific applications. (shrink)

This is a comprehensive study of the English word 'or', and the logical operators variously proposed to present its meaning. Although there are indisputably disjunctive uses of or in English, it is a mistake to suppose that logical disjunction represents its core meaning. 'Or' is descended from the Anglo-Saxon word meaning second, a form which survives in such expressions as "every other day." Its disjunctive uses arise through metalinguistic applications of an intermediate adverbial meaning which is conjunctive rather than (...) disjunctive in character. These conjunctive uses have puzzled philosophers and logicians, and have been discussed extensively under such headings as "free choice permission." This study examines the textbook myths that have clouded our understanding of how or and other "logical" vocabulary comes to have something approaching its logical meaning in natural languages. It considers the various historical conceptions of disjunction and its place in logic from the Stoics to the present day. (shrink)

This paper is a survey of results concerning the disjunction property, Halldén-completeness, and other related properties of intermediate prepositional logics and normal modal logics containing S4.

We systematically study several versions of the disjunction and the existence properties in modal arithmetic. First, we newly introduce three classes $\mathrm {B}$, $\Delta (\mathrm {B})$, and $\Sigma (\mathrm {B})$ of formulas of modal arithmetic and study basic properties of them. Then, we prove several implications between the properties. In particular, among other things, we prove that for any consistent recursively enumerable extension T of $\mathbf {PA}(\mathbf {K})$ with $T \nvdash \Box \bot $, the $\Sigma (\mathrm {B})$ -disjunction (...) property, the $\Sigma (\mathrm {B})$ -existence property, and the $\mathrm {B}$ -existence property are pairwise equivalent. Moreover, we introduce the notion of the $\Sigma (\mathrm {B})$ -soundness of theories and prove that for any consistent recursively enumerable extension of $\mathbf {PA}(\mathbf {K4})$, the modal disjunction property is equivalent to the $\Sigma (\mathrm {B})$ -soundness. (shrink)

Ali Enayat had asked whether two halves of Disjunctive Correctness ([Formula: see text]) for the compositional truth predicate are conservative over Peano Arithmetic (PA). In this paper, we show that the principle “every true disjunction has a true disjunct” is equivalent to bounded induction for the compositional truth predicate and thus it is not conservative. On the other hand, the converse implication “any disjunction with a true disjunct is true” can be conservatively added to [Formula: see text]. The (...) methods introduced here allow us to give a direct nonconservativeness proof for [Formula: see text]. (shrink)

§1 The Disjunctive Conception of Experience Descartes was surely right that while normal waking experience, dreams and hallucinations are characteristically distinguished at a purely phenomenological level, — by contrasts of spatial perspective, coherence, clarity of image, etc., — it is not essential that they be so.1 What is it like for someone who dreams that he is sitting, clothed in his dressing gown, in front of his fire can in principle be subjectively indistinguishable from what it is like to perceive (...) that one is doing so, fully conscious and awake. The same holds for multi-sense hallucination and, it is assumed, would hold of the experience of an envatted brain in the usual postulated scenario. This thought — that normal perceptual experience allows in principle of perfect phenomenological counterfeit — is, to the best of my knowledge, nowhere seriously challenged in John McDowell's writings.2 What he rejects is an idea that builds upon and would be potentially explanatory of it: the Lockean idea that, as far as the states enjoyed by the experiencing subject are concerned, there is actually no generic distinction between dream, hallucination, and wakeful perception: — that one and the same type of state of consciousness is involved in all three cases, and that which (if any) of the three a particular occurrence of the type falls under is a matter of how it is caused. On this model, the distinction between Descartes' notional fully lucid dream and the corresponding raft of perceptions of his dressing-gowned, sedentary state is like that between a certain kind of sunburn and nettle rash. For Disjunctivism, however, the Lockean — as McDowell likes to say, “Highest Common Factor” — conception of perceptual experience and its potential counterfeits is a conceptual error. There is no single type of state of consciousness present in each of dreaming, perceiving and hallucinating, whose instances fall under one or other of those characterisations purely by virtue of their aetiology.. (shrink)