It is not uncommon for philosophers to maintain that one is obliged to believe nothing beyond the observable consequences of a successful scientific theory. This doctrine is variously known as instrumentalism, fictionalism, constructive empiricism, theoretical skepticism and the philosophy of “as if”. The purpose of the present paper is to subject such forms of scientific antirealism to a two-pronged critique. In the first place it is argued that there is no genuine difference between believing a theory and being disposed to use it to make predictions, design experiments, and so on; so traditional instrumentalism is incoherent. In the second place, a retrenched position is considered in which theoretical belief would be tolerated but said to be justified on merely pragmatic, and not epistemic, grounds. In criticizing this point of view it is shown that the onus of proof rests on anyone who maintains it; furthermore, the only possible rationale for it (which is based on underdetermination of theory by data) is described, and various deficiencies in this argument are exposed.

This paper takes issue with Tyler Burge's claim that intentional states are nonindividualistically individuated in cognitive psychology. A discussion of current models of children's acquisition of semantic knowledge is used to motivate a thought-experiment which shows that psychologists working in this area are not committed to describing the concepts children attach to words in terms of the concepts standardly attached to those words in the child's community. The content of the child's representational states are thus not individuated with reference to linguistic environment in the manner that Burge's nonindividualistic view requires. The paper concludes that the explanatory states of cognitive psychology are sometimes individualistically individuated.

The nature of quantum mechanical probability has often seemed mysterious. To shed some light on this topic, the present paper analyzes the logical form of probability assignment in quantum mechanics. To begin the paper, I set out and criticize several attempts to analyze the form. I go on to propose a new form which utilizes a novel, probabilistic conditional and argue that this proposal is, overall, the best rendering of the quantum mechanical probability assignments. Finally, quantum mechanics aside, the discussion here has consequences for counterfactual logic, conditional probability, and epistemic probability.

Husserl's mathematical philosophy of science can be considered an anticipation of the contemporary postpositivistic semantic approach, which regards mathematics and not logic as the appropriate tool for the exact philosophical reconstruction of scientific theories. According to Husserl, an essential part of a theory's reconstruction is the mathematical description of its domain, that is, the world (or the part of the world) the theory intends to talk about. Contrary to the traditional micrological approach favored by the members of the Vienna Circle, Husserl, inspired by modern geometry and set theory, aims at a macrological analysis of scientific theories that takes into account the global structures of theories as structured wholes. This is set in the complementary theories of manifolds and theory forms considered by Husserl himself as the culmination of his formal theory of science.

A number of authors argue that while species are evolutionary units, individuals and real entities, higher taxa are not. I argue that drawing the divide between species and higher taxa along such lines has not been successful. Common conceptions of evolutionary units either include or exclude both types of taxa. Most species, like all higher taxa, are not individuals, but historical entities. Furthermore, higher taxa are neither more nor less real than species. None of this implies that there is no distinction between species and higher taxa; the point is that such a distinction is more subtle than many authors have claimed.

Relationist theories of space or space-time based on embedding of a physical relational system A into a corresponding geometrical system B raise problems associated with the degree of uniqueness of the embedding. Such uniqueness problems are familiar in the representational theory of measurement (RTM), and are dealt with by imposing a condition of uniqueness of embeddings up to composition with an “admissible transformation” of the space B. Friedman (1983) presents an alternative treatment of the uniqueness problem for embedding relationist theories, developed independently of RTM. Friedman's approach differs from that of RTM in securing uniqueness by adding new primitives to the physical system A in contrast to the RTM approach which adds new axioms. Friedman's proposal has recently been developed and defended by Catton and Solomon (1988).

This method of solving the uniqueness problem is here argued to be substantially inferior to the RTM method, both in practice and in principle. In practice we find that in none of the concrete examples offered to illustrate the method is the uniqueness problem actually solved in general. Moreover we find that in the most interesting case (addition to the system A of a finite number of relations of finite degree) the method is in principle incapable of success for mathematical reasons. In addition to these technical difficulties there are compelling methodological reasons for preferring the RTM method to the method of adding primitives.

Mayo (1987) sought to discredit Urbach's (1985) arguments against randomization as a universal requirement in clinical and agricultural trials. The present reply rebuts Mayo's criticisms.