The doctrine that the character of our perceptual knowledge is plastic, and can vary substantially with the theories embraced by the perceiver, has been criticized in a recent paper by Fodor. His arguments are based on certain experimental facts and theoretical approaches in cognitive psychology. My aim in this paper is threefold: (1) to show that Fodor's views on the impenetrability of perceptual processing do not secure a theory-neutral foundation for knowledge; (2) to show that his views on impenetrability are almost certainly false; and (3) to provide some additional arguments for, and illustrations of, the theoretical character of all observation judgments.

This paper defends the Causal Theory of Reference against the recent criticism that it imposes a priori constraints on the aims and practices of science. The metaphysical essentialism of this theory is shown to be compatible with the requirements of naturalistic epistemology. The theory is nevertheless unable to forestall the problem of incommensurability for scientific terms, because it misrepresents the conditions under which their reference is fixed. The resources of the Causal Theory of Reference and of the traditional cluster or “network” theory of meaning for handling problems of commensurability are compared, and an alternative approach is recommended.

David Marr's theory of vision has been widely cited by philosophers and psychologists. I have three projects in this paper. First, I try to offer a perspicuous characterization of Marr's theory. Next, I consider the implications of Marr's work for some currently popular philosophies of psychology, specifically, the “hegemony of neurophysiology view”, the theories of Jerry Fodor, Daniel Dennett, and Stephen Stich, and the view that perception is permeated by belief. In the last section, I consider what the phenomenon of vision must be like for Marr's project to succeed.

The purpose of this paper is to test the contemporary concept of biological species against some of the problems caused by treating species as spatiotemporally extended entities governed by criteria of persistence, identity, etc. After outlining the general problem of symmetric division in natural objects, I set out some useful distinctions (section 1) and confirm that species are not natural kinds (section 2). Section 3 takes up the separate issue of species definition, focusing on the Biological Species Concept (BSC). Sections 4 and 5 examine the matter of species identity over space and time respectively, as determined by the BSC. Both gradualistic and punctuated equilibrium models of speciation are discussed. In section 6 I argue that the BSC fails to determine adequate criteria for dealing with certain kinds of speciation. Section 7 moves speculatively beyond the BSC to a brief examination of alternatives.

The commensurability of two theories can be defined (relative to a given set of questions) as the ratio of the total information of their shared answers to the total information of the answers yielded by the two theories combined. Answers should be understood here as model consequences (in the sense of the author's earlier papers), not deductive consequences. This definition is relative to a given model of the joint language of the theories, but can be generalized to sets of models. It turns out to capture also the idea of incommensurability as conceptual alienation. Incommensurability so defined does not imply incomparability.

Physicalism is an empirical theory of the mind and its place in nature. So the physicalist must show that current neuroscience does not falsify physicalism, but instead supports it. Current neuroscience shows that a nervous system is what I call a vector function system. I provide a brief outline of the resources that empirical research has made available within the constraints of the vector function approach. Then I argue that these resources are sufficient, indeed apt, for the physicalist enterprise, by offering a vector functional, hence physicalist, theory of the percept—the perceptual experience itself, a paradigm of phenomenally immediate, introspectively accessible consciousness.

The formal time symmetry of the quantum measurement process is extensively discussed. Then, the origin of the alleged association between a fixed temporal direction and quantum measurements is investigated. It is shown that some features of such an association might arise from epistemological rather than purely physical assumptions. In particular, it is brought out that a sequence of statements bearing on quantum measurements may display intrinsic asymmetric properties, irrespective of the location of corresponding measurements in time t of the Schrödinger equation. The situation of an observer performing two measurements in two opposite directions of t is eventually investigated. Essential differences are found between two descriptions of this situation: the internal one (taking only into account what is recorded in the observer's memory) and the external one (whereby the observer is considered as a quantum system ruled by the Schrödinger equation). Finally, a method allowing several observers to establish a correspondence between their memory sizes is analyzed. The most important facts that usually lead to the associating of a preferential temporal direction with quantum measurements may be inferred from this correspondence.

Churchland's paper “Perceptual Plasticity and Theoretical Neutrality“ offers empirical, semantical and epistemological arguments intended to show that the cognitive impenetrability of perception “does not establish a theory-neutral foundation for knowledge” and that the psychological account of perceptual encapsulation that I set forth in The Modularity of Mind “[is] almost certainly false“. The present paper considers these arguments in detail and dismisses them.

A plurality of axiomatic systems can be interpreted as referring to one and the same mathematical object. In this paper we examine the relationship between axiomatic systems and their models, the relationships among the various axiomatic systems that refer to the same model, and the role of an intelligent user of an axiomatic system. We ask whether these relationships and this role can themselves be formalized.

This paper challenges some leading views about the conditions under which the ascription of beliefs and desires can make sense of, or provide reasons for, a creature's behavior. I argue that it is unnecessary for behavior to proceed from beliefs and desires according to the principles of logic and decision theory, or even from principles that generally get things right. I also deny that it is necessary for behavior to proceed from principles that, though perhaps subrational, are similar to those that we ourselves use. I then propose some conditions that are considerably weaker, and argue that they fulfill the descriptive and explanatory requirements of intentional ascription.

There is sufficient evidence at present to justify the belief that the universe began to exist without being caused to do so. This evidence includes the Hawking-Penrose singularity theorems that are based on Einstein's General Theory of Relativity, and the recently introduced Quantum Cosmological Models of the early universe. The singularity theorems lead to an explication of the beginning of the universe that involves the notion of a Big Bang singularity, and the Quantum Cosmological Models represent the beginning largely in terms of the notion of a vacuum fluctuation. Theories that represent the universe as infinitely old or as caused to begin are shown to be at odds with or at least unsupported by these and other current cosmological notions.

Sober (1984) has considered the problem of determining the evidential support, in terms of likelihood, for a hypothesis that is incomplete in the sense of not providing a unique probability function over the event space in its domain. Causal hypotheses are typically like this because they do not specify the probability of their initial conditions. Sober's (1984) solution to this problem does not work, as will be shown by examining his own biological examples of common cause explanation. The proposed solution will lead to the conclusion, contra Sober, that common cause hypotheses explain statistical correlations and not matchings between event tokens.

Causal decision theory produces decision instability in cases such as Death in Damascus where a decision itself provides evidence concerning the utility of options. Several authors have proposed ways of handling this instability. William Harper (1985 and 1986) advances one of the most elegant proposals. He recommends maximizing causal expected utility among the options that are causally ratifiable. Unfortunately, Harper's proposal imposes certain restrictions; for instance, the restriction that mixed strategies are freely available. To obtain a completely general method of handling decision instability, I step outside the confines of pure causal decision theory. I introduce a new kind of backtracking expected utility and propose maximizing it among the options that are causally ratifiable. In other words, I propose a hierarchical maximization of (1) conditional causal expected utility and (2) the new backtracking expected utility. I support this proposal with some intuitive considerations concerning the distinction between optimality and conditional optimality. And I prove that the proposal yields a solution in every finite decision problem.

Fine has recently proved the surprising result that satisfaction of the Bell inequality in a Clauser-Horne experiment implies the existence of joint probabilities for pairs of noncommuting observables in the experiment. In this paper we show that if probabilities are interpreted in the von Mises-Church sense of relative frequencies on random sequences, a proof of the Bell inequality is nonetheless possible in which such joint probabilities are assumed not to exist. We also argue that Fine's theorem and related results do not impugn the common view that local realists are committed to the Bell inequality.

Professor Grünbaum's much-discussed refutation of Zeno's metrical paradox turns out to be ad hoc upon close examination of the relevant portion of measure theory. Although the modern theory of measure is able to defuse Zeno's reasoning, it is not capable of refuting Zeno in the sense of showing his error. I explain why the paradox is not refutable and argue that it is consequently more than a mere sophism.

A tempting argument for human rationality goes like this: it is more conducive to survival to have true beliefs than false beliefs, so it is more conducive to survival to use reliable belief-forming strategies than unreliable ones. But reliable strategies are rational strategies, so there is a selective advantage to using rational strategies. Since we have evolved, we must use rational strategies. In this paper I argue that some criticisms of this argument offered by Stephen Stich fail because they rely on unsubstantiated interpretations of some results from experimental psychology. I raise two objections to the argument: (i) even if it is advantageous to use rational strategies, it does not follow that we actually use them; and (ii) natural selection need not favor only or even primarily reliable belief-forming strategies.

Support functions s(h,e) = p(h|e) – p(h) are widely used in discussion of explanation, causality and, recently, in connection with the possibility or otherwise of probabilistic induction. With this latter application in view, a rather complete analysis of the variety of support functions, their interrelationships and their “non-deductive” and “inductive” components is presented. With the restriction to two propositions, three variable probabilities are enough to discuss such problems. The analysis is illustrated by graphs, a Venn diagram and by using the Laplace Rule of Succession as an illustrative example. It is concluded that within this framework one cannot prove or disprove the possibility of probabilistic induction.

Benton Stidd has defended the position that punctuationists are not wrong about the inadequacy of the synthetic theory of evolution for explaining evolution. The thrust of his defense is that arguments to the contrary by Thompson (1983a) involve a rational reconstruction along logical empiricist lines, which is insensitive to historical and social forces in a way that the Kuhnian Weltanschauung view that he espouses is not. I argue in this paper that Stidd has entirely misunderstood my arguments, that the soundness of my arguments does not depend on acceptance of logical empiricism (they are just as sound on a Kuhnian view), and that Stidd fails to establish that punctuated equilibria is a new “paradigm“.

A common view among statisticians is that convergence (which statisticians call consistency) is a necessary property of an inference rule or estimator. In this paper, this view is challenged by appeal to an example in which a rule of inference has a likelihood rationale but is not convergent. The example helps clarify the significance of the likelihood concept in statistical inference.

When can one say that a new theory is truer than the old one it contradicts, even though neither is absolutely true? We are primarily concerned with the case in which the conflicting theories offer answers to the same questions, and so we do not introduce considerations of “logical width”. We propose that part of the new theory is truer than part of the old one when the former part gets right whatever the latter part got right while the former does not make any new mistakes. Pragmatic considerations will determine the relative importance of whatever new mistakes the new theory does make as a whole. To avoid artificial counterexamples, we restrict the parts compared to those that are “convex”. A “convex” theory is one that holds in all cases intermediate between any two cases in which it holds.