半结构化概率论辩

群组方法概率论辩是一种建模因知识不确定性而导致论证不确定性的有效方法。目前已有工作假设所有论证之间具有独立性,悬隔了论证之间的支持关系,在语义的解释上造成三个与直觉不甚相符的问题:第一,存在接受一个论证却不接受其子论证的可能性;第二,存在可能接受子论证间相互矛盾的论证;第三,论证受到其子论证的保护作用可能被削弱。针对这三个问题,在群组方法概率论辩的基础上引入直接子论证关系,建立半结构化概率论辩框架,恰当地修补原有群组方法的不足。     

Ability-based objections to no-best-world arguments

In the space of possible worlds, there might be a best possible world (a uniquely best world or a world tied for best with some other worlds). Or, instead, for every possible world, there might be a better possible world. Suppose that the latter is true, i.e., that there is no best world. Many have thought that there is then an argument against the existence of God, i.e., the existence of an omnipotent, omniscient and morally perfect being; we will call such arguments no-best-world arguments. In this paper, we discuss ability-based objections to such arguments; an ability-based objection to a no-best world argument claims that the argument fails because one or more of its premises conflict with a plausible principle connecting the applicability of some type of moral evaluation to the agent’s possession of a relevant ability. In particular, we formulate and evaluate an important new ability-based objection to the most promising no-best world argument.     

IN DEFENCE OF MAGICAL ERSATZISM

David Lewis' objection to a generic theory of modality which he calls 'magical ersatzism' is that its linchpin, a relation he calls 'selection', must be either an internal or an external relation, and that this is unintelligible either way. But the problem he points out with classifying selection as internal is really just an instance of the general problem of how we manage to grasp underdetermined predicates, is not peculiar to magical ersatzism, and is amenable to some familiar solutions. He provides no compelling grounds for thinking that classifying selection as external is unintelligible, and his argument has a false presupposition. I conclude that magical ersatzism is still a viable option in the metaphysics of modality.     

Propositions, semantic values, and rigidity

Jeffrey King has recently argued: (i) that the semantic value of a sentence at a context is (or determines) a function from possible worlds to truth values, and (ii) that this undermines Jason Stanley's argument against the rigidity thesis, the claim that no rigid term has the same content as a non-rigid term. I show that King's main argument for (i) fails, and that Stanley's argument is consistent with the claim that the semantic value of a sentence at a context is (or determines) a function from worlds to truth values.     

Three arguments for humility

Ramseyan humility is the thesis that we cannot know which properties realize the roles specified by the laws of completed physics. Lewis seems to offer a sceptical argument for this conclusion. Humean fundamental properties can be permuted as to their causal roles and distribution throughout spacetime, yielding alternative possible worlds with the same fundamental structure as actuality, but at which the totality of available evidence is the same. On the assumption that empirical knowledge requires evidence, we cannot know which of these worlds is actual. However, Lewis also appeals to a range of familiar semantic principles when framing his argument, which leads some authors to suppose that he can also plausibly be interpreted as offering a purely semantic argument for humility in addition. In this paper I grant that these arguments are Lewisian, but argue that Lewis is also committed to a theory of mind that licenses a purely metaphysical argument for humility based on the idea that mental properties supervene on fundamental structure. Given that knowing which x is the F requires knowing that a is the F, the supposition that we could come to know which properties actually occupy the fundamental roles entails differences in mental properties between worlds with the same fundamental structure, violating supervenience. Humility follows right away, without any further epistemic or semantic principles. This argument is immune to almost every way of rebutting the sceptical and semantic arguments; conversely, almost every way of rebutting the metaphysical argument tells equally against the others.     

The best of all possibleworlds

The Argument from Inferiority holds that our world cannot be the creation of an omnipotent and omnibenevolent being; for if it were, it would be the best of all possible worlds, which evidently it is not. We argue that this argument rests on an implausible principle concerning which worlds it is permissible for an omnipotent being to create: roughly, the principle that such a being ought not to create a non-best world. More specifically, we argue that this principle is plausible only if we assume that there is a best element in the set of all possible worlds. However, as we show, there are conceivable scenarios in which that assumption does not hold.     

Brown on Mackie: Echoes of the Lottery Paradox

In “The possibility of morality,” Phil Brown considers whether moral error theory is best understood as a necessary or contingent thesis. Among other things, Brown contends that the argument from relativity, offered by John Mackie—error theory’s progenitor—supports a stronger modal reading of error theory. His argument is as follows: Mackie’s is an abductive argument that error theory is the best explanation for divergence in moral practices. Since error theory will likewise be the best explanation for similar divergences in possible worlds similar to our own, we may conclude that error theory is true at all such worlds, just as it is in the actual world. I contend that Brown’s argument must fail, as abductive arguments cannot support the modal conclusions he suggests. I then consider why this is the case, concluding that Brown has stumbled upon new and interesting evidence that agglomerating one’s beliefs can be epistemically problematic—an issue associated most famously with Henry Kyburg’s lottery paradox.     

Is Skepticism about Self-Knowledge Coherent?

In previous work I argued that skepticism about the compatibility ofanti-individualism with self-knowledge is incoherent. Anthony Brueckner isnot convinced by my argument, for reasons he has recently explained inprint. One premise in Brueckner's reasoning is that a person'sself-knowledge is confined to what she can derive solely from herfirst-person experiences of using her sentences. I argue that Brueckner'sacceptance of this premise undermines another part of his reasoning – hisattempt to justify his claims about what thoughts our sincere utterances ofcertain sentences would express in various possible worlds. I describe aweird possible world in which a person who uses Brueckner's reasoning endsup with false beliefs about what thoughts her sincere utterances of certainsentences would express in various possible worlds. I recommend that wereject Brueckner's problematic conception of self-knowledge, and adopt onethat better fits the way we actually ascribe self-knowledge.     

Books Received

This paper is an attempt to answer the question, ‘could there be causation in a timeless world?’ My conclusion: tentatively, yes. The paper and argument have three parts. Part one introduces salient issues and spells out the importance of this (initially somewhat baroque seeming) line of investigation. Section two of the paper reviews recent arguments due to Baron and Miller, who argue in favour of the possibility of causation in a timeless world, and looks to reject their arguments developed there. Section three is a response to a response. In their, Baron and Miller also argue that an argument in favour of the possibility of causation at timeless worlds, that I put forward, is an argument that fails. In section three, my response to Baron and Miller is that their argument against me succeeds, but that there is a nearby argument that we can appeal to in order to demonstrate the possibility of causation at timeless worlds.     

Omissions and Preventions as Cases of Genuine Causation

Abstract

Timothy Williamson has defended the claim that any philosophically satisfying conception of modality that encompasses possible worlds semantics (PWS) commits us to the Barcan Formula. His argument depends on the assumption that the domain of what there is (the domain of the actual world) has to be identified with the domain D(@), where @ is the index or possible world that in PWS represents, or stands for, the actual world. I work out an interpretation of the relation between PWS and possible worlds terminology that makes it plausible to reject that assumption.     

Why ‘Is’ Must Entail ‘Ought’

I argue below for the view that non-moral truths entail moral ones. I first argue that moral claims do have truth values which are objectively true or false. I then argue that this objectivism does not entail non-relativism. I produce a simple possible worlds argument for the entailment view. I then give some examples where p entails q but many intelligent people have thought it does not, and where it does not, but many intelligent people have thought that it does. I also try to evaluate a somewhat neglected argument by Hume. In the final section, I further consider some moral and meta-moral opinions.     

A Defense of Egalitarianism

Recently in this journal, Michael Huemer has attempted to refute egalitarianism. His strategy consists in: first, distinguishing between three possible worlds (one with an equal distribution of well-being, one with an unequal distribution at every moment but with an equal distribution overall, and one with an unequal distribution at every moment as well as overall); second, showing that the first world is equal in value to the second world; third, dividing the second and third worlds into two temporal segments each, then showing that none of the temporal segments possesses greater moral value than any other, thereby demonstrating that the second and third worlds as a whole are equal in value; and finally, concluding that none of the three worlds has more value than any other. The present article rebuts Huemer’s critique of egalitarianism first, and most importantly, by showing that his core argument rests upon an equivocation, and second, by refuting his supplementary arguments.     

Tracing and heavenly freedom

A new version of the ontological argument for the existence of God is outlined and examined. After giving a brief account of some traditional ontological arguments for the existence of God, where their defects are identified, it is explained how this new argument is built upon their foundations and surmounts their defects. In particular, this version uses the resources of impossible worlds to plug the common escape route from standard modal versions of the ontological argument. After outlining the nature of impossible worlds, and motivating the need for positing them, the new argument is delineated and its premises justified. It is taken for granted that the argument cannot be sound, since it would prove too much. However, its premises are all plausible, and their denial promises to have significant ramifications. Several intuitive lines of objections are then explored in order to illuminate their shortcomings. The puzzle that the argument poses is therefore not whether the argument is sound, for it clearly cannot be. Rather, it is to place pressure on its plausible premises, so some plausible account of how the argument fails can be identified, and that the devising of such an account promises to be insightful. In the process, we should gain an improved understanding of how such ontological arguments work.     

Relativism and Two Kinds of Branching Time

This essay examines the case for relativism about future contingents in light of a distinction between two ways of interpreting the ‘branching time’ framework. The first step of the relativist argument is to argue for the ‘Non-Determination Thesis’, the view that there is no unique actual future. The second step is to argue from the Non-Determination Thesis to relativism. I show that first step of this argument fails. But despite that result, the second step is still of interest, because one might hold the Non-Determination Thesis on alternative grounds. I then argue that whether the second step of the argument succeeds depends on how the branches in question are interpreted. If the branches are ersatz possible worlds, then the argument for relativism might go through. But if the branches are concrete parts of a ‘branching multiverse’, then the argument for relativism turns out to make implausible assumptions about the nature of personal identity over time.     

Reasoning About Collectively Accepted Group Beliefs

A proof-theoretical treatment of collectively accepted group beliefs is presented through a multi-agent sequent system for an axiomatization of the logic of acceptance. The system is based on a labelled sequent calculus for propositional multi-agent epistemic logic with labels that correspond to possible worlds and a notation for internalized accessibility relations between worlds. The system is contraction- and cut-free. Extensions of the basic system are considered, in particular with rules that allow the possibility of operative members or legislators. Completeness with respect to the underlying Kripke semantics follows from a general direct and uniform argument for labelled sequent calculi extended with mathematical rules for frame properties. As an example of the use of the calculus we present an analysis of the discursive dilemma.     

Externalism and Token‐Identity

This study has two goals. The first is to identify three desiderata required for a successful defense of a version of nonreductive physicalism: semantic externalism, token‐identity between mental and physical events, and nonrelational type‐individuation of physical states. In this context, the paper also presents a refutation of recent challenges to content‐externalism by those who attempt to resuscitate internalism by focusing on narrow content associated with the fundamental phenomenology, rather than the intentionality, of mental states. The second goal is to defend the token‐identity thesis from Tyler Burge's argument to the effect that token‐identity is incompatible with semantic externalism. An account is also offered as to why Burge's argument, albeit fallacious, might seem persuasive under a certain interpretation of possible worlds.     

How Not to Argue for Incompatibilism

Ted A. Warfield has recently employed modal logic to argue that compatibilism in the free-will/determinism debate entails the rejection of intuitively valid inferences. I show that Warfield's argument fails. A parallel argument leads to the false conclusion that the mere possibility of determinism, together with the necessary existence of any contingent propositions, entails the rejection of intuitively valid inferences. The error in both arguments involves a crucial equivocation, which can be revealed by replacing modal operators with explicit quantifiers over possible worlds. I conclude that the modal-logical apparatus used by Warfield obscures rather than clarifies, and distracts from the real philosophical issues involved in the metaphysical debate. These issues cannot be settled by logic alone.     

Everettian quantum mechanics without branching time

In this paper I assess the prospects for combining contemporary Everettian quantum mechanics (EQM) with branching-time semantics in the tradition of Kripke, Prior, Thomason and Belnap. I begin by outlining the salient features of ??decoherence-based?? EQM, and of the ??consistent histories?? formalism that is particularly apt for conceptual discussions in EQM. This formalism permits of both ??branching worlds?? and ??parallel worlds?? interpretations; the metaphysics of EQM is in this sense underdetermined by the physics. A prominent argument due to Lewis (On the Plurality of Worlds, 1986) supports the non-branching interpretation. Belnap et?al. (Facing the Future: Agents and Choices in Our Indeterministic World, 2001) refer to Lewis?? argument as the ??Assertion problem??, and propose a pragmatic response to it. I argue that their response is unattractively ad hoc and complex, and that it prevents an Everettian who adopts branching-time semantics from making clear sense of objective probability. The upshot is that Everettians are better off without branching-time semantics. I conclude by discussing and rejecting an alternative possible motivation for branching time.     

Modal Rationalism and Modal Monism

Modal rationalism includes the thesis that ideal primary positive conceivability entails primary possibility. Modal monism is the thesis that the space of logically possible worlds is coextensive with the space of metaphysically possible worlds. In this paper I explore the relation between the two theses. My aim is to show that the former thesis implies the latter thesis, and that problems with the latter make the former implausible as a complete picture of the epistemology of modality. My argument explores the relation between logical modality and metaphysical modality.

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