EPISTEMIC COHERENTISM AND THE ISOLATION OBJECTION

Paul K. MOSER Loyola University of Chicago

The isolation objection, as standardly formulated, claims that the coherence theory of empirical epistemic justification (or 'epistemic coherentism' for short) divorces empirical justification from the empirical world. In this form the isolation objection is obviously too rough to threaten any coherence theory. But in what follows I shall argue that there is aversion of this objection that does challenge epistemic coherentism. The basic point of this objection, as I shall explain, is that epistemic coherentism divorces empirical justification from empirically reliable belief. But before developing this point, we need to attend to so me preliminaries.

I Let us begin by clarifying the basic idea of epistemic coherentism. The leading contemporary versions of coherentism are .holistic insofar as they define 'coherence' as a relation between a candidate belief and the set of all the beliefs a person antecedently holds. Holistic coherentism conflicts with any axiomatic conception of empirical justification depicting the fundamental relation between justified beliefs as one of linear dependence with derivative beliefs depending on foundational beliefs. Rather, it provides a network conception of justification depicting the fundamental relation be• tween justified beliefs as one of mutual support. The following principle, then, will provide a useful schema for a coherence theory of empirical justification: 1 CT. A person S is justified in believing a proposition P if and only if P coheres with the beliefs bel on ging to a belief-system of kind K that

1. This schema is suggested by Keith Lehrer, Knowledge (Oxford: Claren• don Press, 1974), p. 154. 84 does not require non-inferentially justified, foundational propositions for the justification of any proposition. In accepting this schema, the coherentist must meet two basic requirements. He must provide us with an account of the relation called 'coherence', and he must specify the kind of system with which a jusitified proposition must cohere. Coherence theorists gene rally agree that the kind of coherence sufficient for empirical jusitifcation is not merely logical consistency. In fact, so me coherentists, such as Brand Blanshard, construe coherence as a relation of necessary connection. On Blanshard's theory, a proposition P coheres with other propositions of a system K if and only if P logically entails and is logically entailed by every other proposition in K. 2 But it seems implausible to hold that this kind of coherence is necessary for empirical justification, since typically we assume that propositions about unrelated perceptual objects can be justified for a person even if they do not entail each other. Similarly, it seems im plausible to hold that such coherence is sufficient for empirical justification, mainly because of the following familiar problem. Taking any consistent system of contingent propositions marked by coherence in Blanshard's sense, one can form an equally coherent system simply by negating each proposition in the first system. But the new system will contradict everything the firstsystem states about the empirical world. Hence, if Blanshard's kind of logical coherence is sufficient for empirical justification, any con• tingent proposition justified for a person will be such that its denial is similarly justified. Surely this problem, in conjunction with the preceding problem, should advise us against construing coherence as mutual logical entailment. Such problems have led many coherentists to connect coherence with explanation, thus producing explanatory coherence theories.3 2. See Blanshard, The Nature of Thought, 2 vols. (London: Allen & Unwin, 1939), 2:265-66. A useful discussion of Blanshard's theory is Nicholas Rescher's "Blanshard and the Coherence Theory of Truth", in The Philosophy of Brand Blanshard, ed. Paul Schilpp (LaSalle, IL: Open Court, 1980), pp. 574-88. 3. Variations on explanatory coherentism appear, for instance, in the writings of W.V. Quine, Wilfrid Sellars, and Gilbert Harman. See Quine and J.S. Ullian, The Web of Belief, 2d ed. (New York: Random House, 1978); Sellars, "Some Reflections on Language Games", in Science, Perception and