John Divers

Kant states that necessity and strict universality are criteria of a priori knowledge. Interpreting this dictum standardly and straightforwardly in respect of necessity, it is inconsistent with there being necessary a posteriori truths or contingent a priori truths (cf Kripke). This straightforward interpretation may convict Kant of understandable error (at worst) in the case of necessity, but it is so uncharitable in the case of strict universality that we ought to seek an alternative. I offer a charitable interpretation of the doctrine that necessity and strict universality are sufficient conditions of a priority, commenting briefly on comparable necessary conditions.

In this reply, we defend our argument for the incompleteness of Genuine Modal Realism against Paseau's criticisms. Paseau claims that isomorphic set of worlds represent the same possibilities, but not only is this implausible, it is inimical to the target of our paper: Lewis's theory of possible worlds. We argue that neither Paseau's model-theoretic results nor his comparison to arithmetic carry over to GMR. We end by distinguishing two notions of incompleteness and urge that, for all that Paseau has said, GMR remains incomplete in the relevant sense.

  The modal primitivist who takes a sentential possibility operator as her only modal resource can provide adequate representations of the familiar concepts of weak, strong and global supervenience. The primitivist representations of these concepts can be applied to provide adequate interpretations of speciflc supervenience theses which will be considered. Moreover the modal primitivist is no better and no worse placed than the genuine modal realist to present supervenience as a simple and unifled notion. Therefore, Lewis is unjustified in claiming that a genuine modal realist approach to the analysis of the concept of supervenience is superior to a modal primitivist approach

In section 1 I motivate and execute the presentation of a well-defined Lewisian conception of analysis and of what it would be to analyse modality successfully. That conception is then put to two applications. In section 2 various inadequacies are exposed in a (recently popular) separatist approach to the understanding and/or evaluation of Lewis's analysis of modality. Section 3 provides a defence against a resilient argument for the claim that Lewis's analysis of modality cannot be fully reductive while also dealing adequately with alien possibility.

If a possible-worlds semantic theory for modal logics is pure, then the assertion of the theory, taken at face-value, can bring no commitment to the existence of a plurality of possible worlds (genuine or ersatz). But if we consider an applied theory (an application of the pure theory) in which the elements of the models are required to be possible worlds, then assertion of such a theory, taken at face-value, does appear to bring commitment to the existence of a plurality of possible worlds. Or at least that is so if the applied theory is adequate. For an applied possible-worlds semantic theory that is constrained to contain only one-world models is bound to deliver results on validity, soundness and completeness that are apt to seem disastrous. I attempt to steer a course between commitment to the existence of a plurality of possible worlds and commitment to such a disastrous applied possible-worlds semantics by noting, and developing, the position of one who asserts such a theory at face-value but who remains agnostic about the existence of other (non-actualized) possible worlds. Thus, a novel interpretation of applied possible-worlds semantics is offered on which we may lay claim to whatever benefits such a theory offers while avoiding realism about (other) possible worlds. Thereby, the contention that applied possible-worlds semantics gives us reason to be realists about possible worlds is (further) undermined.

This chapter has three principal aims. Firstly, to promote interest in the question of the function, or utility, of judgements of modality. Secondly, to endorse an alternative to orthodox contemporary methodology, advocating that we prioritize the question of function in modal philosophy. Thirdly, to consider among our modal judgements exactly which are the proper and exact source of various different kinds of substantial philosophical commitments in ontology, epistemology, and elsewhere. An illustration is offered, in the de dicto case, of how minimal a philosophical theory of modality might be if constructed properly, and carefully, according to functional methodology.

Colin McGinn proposes that acceptance of the supervenience of the modal on the actual is the natural form of expression of a non-objectual realism about modality. Here, some of the difficulties that arise in applying theses of supervenience to the modal-actual case are discussed. It is then argued: 1)that the truth of many such theses is determined on uncontroversial modal logical and conceptual grounds, and 2) that this and other independent considerations render it highly implausible that the affirmation of modal-actual supervenience amounts to a modal realism

The principle of modal ubiquity - that every truth is necessary or contingent - and the validity of possibility introduction, are principles that any modal theory suffers for failing to accommodate. Advanced modal claims are modal claims about entities other than spatiotemporally unified individuals (perhaps, then, spatiotemporally disunified individuals, sets, numbers, properties, propositions and events). I show that genuine modal realism, as it has thus far been explicitly developed, and in so far as it deals with advanced modal claims, cannot accommodate the principles in question. On behalf of the genuine modal realist I motivate and propose a redundancy interpretation of advanced possibility claims and extend that interpretation to the cognate cases of necessity, impossibility and contingency. I then show that the problematic principles as they apply to advanced modal claims can be derived from these interpretations. I show further how the proposed interpretation enables the genuine modal realist to deal with a number of objections that centre on the alleged inadequacy of the genuine modal realist's expressive resources. I conclude that genuine modal realism emerges the stronger for having been shown capable of dealing with advanced modal claims on the basis of no conceptual and ontological resources beyond those it requires to deal with ordinary modal claims.

The modal antirealist, as presented here, aims to secure at least some of the benefits associated with talking in genuine modal realist terms while avoiding commitment to a plurality of Lewisian (or ersatz) worlds. The antirealist stance of agnosticism about other worlds combines acceptance of Lewis's account of what world-talk means with refusal to assert, or believe in, the existence of other worlds. Agnosticism about other worlds does not entail a comprehensive agnosticism about modality, but where such agnosticism about modality is enforced, the aim of the agnostic programme is to show that it is not detrimental to our modal practices. The agnostic programme consists in an attempt to demonstrate the rational dispensability of that disputed class of modal beliefs which the agnostic eschews, but which are held by the realist and the folk. Here I attempt to motivate, describe, and illustrate such an agnostic antirealist programme in modal philosophy