Bas C. Van Fraassen

There are striking differences between the scientific theoretical description of the world and the way it seems to us. The consequent task of relating science to ’the world we live in’ has been a problem throughout the history of science. But have we made this an impossibility by how we formulate the problem? Some say that besides the successive world-pictures of science there is the world-picture that preceded all these and continues to exist by their side, elucidated by more humanistic philosophers. Wilfrid Sellars codified this conviction in his dichotomy of scientific image and manifest image. Others say that all our world-pictures are transient, evolve, conflict with and replace each other, undergo violent revolutions as well as periods of normal development, and may be incommensurable, allowing of no meaningful dialogue. All such formulations may themselves be tendentious metaphysics, full of false contrasts. Insistence on a radical separation between science and what we have apart from science, on the impossibility of accommodating science without surrender, may be a way of either idolizing or demonizing science rather than understanding it.

In his widely influential two-volume work, Warrant: The Current Debate and Warrant and Proper Function, Alvin Plantinga argued that warrant is that which explains the difference between knowledge and true belief. Plantinga not only developed his own account of warrant but also mapped the terrain of epistemology. Motivated by Plantinga's work, fourteen prominent philosophers have written new essays investigating Plantingian warrant and its contribution to contemporary epistemology. The resulting collection, representing a broad array of views, not only gives readers a critical perspective on Plantinga's landmark work, but also provides in one volume a clear statement of the variety of approaches to the nature of warrant within contemporary epistemology, and to the connections between epistemology and metaphysics. Positions covered include internalism and externalism, reliabilism, coherentism and foundationalism, virtue theories, and defensibility theories. Alvin Plantinga responds to the essays in his own contribution.

There are a number of dimensions to the realism-nominalism controversy. The topics of debate comprise: necessary connections and causality, dispositions and counterfactuals, space and time, the existence of abstract entities and mathematical objects, the existence of the theoretical entities of science. On all these except the last, Sellars takes a non-realist line: and on all these except the last, I agree with him to the extent that I presently have an opinion on them. But Sellars is a scientific realist, encapsulating this realism in the dictum: “to have good reason for holding a theory is ipso facto to have good reason for holding that the entities postulated by the theory exist”.

ABSTRACT For changing opinion, represented by an assignment of probabilities to propositions, the criterion proposed is motivated by the requirement that the assignment should have, and maintain, the possibility of matching in some appropriate sense statistical proportions in a population. This ‘tracking’ criterion implies limitations on policies for updating in response to a wide range of types of new input. Satisfying the criterion is shown equivalent to the principle that the prior must be a convex combination of the possible posteriors. Furthermore, this is equivalent to the requirement that prior expected values must fall inside the range spanned by possible posterior expected values. The tracking criterion is liberal; it allows for, but does not require, a policy such as Bayesian conditionalization, and can be offered as a general constraint on policies for managing opinion over time. Examples are given of non-Bayesian policies, both ones that satisfy and ones that violate the criterion. _1_ Introduction _2_ Alternative Updating Policies _3_ Modelling the Situation for Normal Updating _4_ Tracking: A Criterion for Updating Policies _5_ Tracking: Precise Formulation and Relation to Convexity _6_ The Spanning Criterion _7_ Non-Bayesian Policies that Satisfy the Spanning and Tracking Criteria _8_ Policies that Violate the Spanning and Tracking Criteria Appendix Appendix

What is the empirical content of a theory? If a theory is identified with one of its linguistic formulations, the only available answers allow for no non‐trivial distinction between empirical and non‐empirical content. The restriction of such a formulated theory to a narrow ‘observational’ vocabulary is not a description of the observable part of the world but a hobbled and hamstrung description of its entire domain, still with non‐empirical implications. Viewing a theory as identified through the family of its models––the structures it makes available for modelling the phenomena––yields a new approach. The distinctions so made are illustrated with Newton's physics, absolute versus relative motion, nineteenth‐ century ether theory of electromagnetism, and quantum mechanics. A hermeneutic circle in the interpretation is noted, and the theory‐independence of the observable/unobservable distinction maintained.

Explanatory power is a complex theoretical virtue, not reducible to empirical strength or adequacy, which includes other virtues as its own preconditions. Since this virtue provides one of the main criteria by which theories are evaluated, it presents thus a challenge to any empiricist account of science. After a critical account of attempted explications of the concept of scientific explanation, this chapter offers a pragmatic account that identifies explanations with answers to why‐questions. Since such questions are set by the questioner, and have their family of relevant direct answers determined by the presuppositions, values, and interests involved in the questioning, that makes explanation relative to contextual factors. On this understanding, evaluations of scientific explanation cannot play the role required for their use in support of scientific realism––and, incidentally, the large array of standard puzzles in the literature on this subject are solved.

I exist, but I am not a thing among things; X exists if and only if there is something such that it=X. This is consistent, and it is a view that can be supported. Calvino’s novel The Non‐Existent Knight can be read so as to illustrate this view. But what is my relation to the things there are if I am not identical with any of them – things such as my arms, my garden, the city I live in? I name this the Gurduloo problem, after the Knight’s page. This relation must be one that admits of degrees; I suggest that we say that I manifest myself through the things thus associated with me. Several pseudo‐problems, pertaining to volitional action, supervenience, observability, and the emergence of consciousness, dissolve upon inspection.

After Hume, attempts to forge an empiricist epistemology have taken three forms, which I shall call the First, Middle, and Third Way. The First still attempts an a priori demonstration that our cognitive methods satisfy some criterion of adequacy. The Middle Way is pursued under the banners of naturalism and scientific realism, and aims at the same conclusion on non-apriori grounds. After arguing that both fail, I shall describe the general characteristics of the Third Way, an alternative epistemology suitable for empiricism