ABSTRACT. May scientists rely on substantive, a priori presuppositions? Quinean naturalists say "no," but Michael Friedman and others claim that such a view cannot be squared with the actual history of science. To make his case, Friedman offers Newton's universal law of gravitation and Einstein's theory of relativity as examples of admired theories that both employ presuppositions (usually of a mathematical nature), presuppositions that do not face empirical evidence directly. In fact, Friedman claims that the use of such presuppositions is a hallmark of "science as we know it." But what should we say about the special sciences, which typically do not rely on the abstruse formalisms one finds in the exact sciences? I identify a type of a priori presupposition that plays an especially striking role in the development of empirical psychology. These are ontological presuppositions about the type of object a given science purports to study. I show how such presuppositions can be both a priori and rational by investigating their role in an early flap over psychology's contested status as a natural science. The flap focused on one of the field's earliest textbooks, William James's Principles of Psychology. The work was attacked precisely for its reliance on a priori presuppositions about what James had called the "mental state," psychology's (alleged) proper object. I argue that the specific presuppositions James packed into his definition of the "mental state" were not directly responsible to empirical evidence, and so in that sense were a priori; but the presuppositions were rational in that they were crafted to help overcome philosophical objections (championed by neo-Hegelians) to the very idea that there can be a genuine science of mind. Thus, my case study gives an example of substantive, a priori presuppositions being put to use—to rational use—in the special sciences. In addition to evaluating James's use of presuppositions, my paper also offers historical reflections on two different strands of pragmatist philosophy of science. One strand, tracing back through Quine to C. S. Peirce, is more naturalistic, eschewing the use of a priori elements in science. The other strand, tracing back through Kuhn and C. I. Lewis to James, is more friendly to such presuppositions, and to that extent bears affinity with the positivist tradition Friedman occupies.

ABSTRACT.  The canonical empiricists are Locke, Berkeley, and Hume. But these figures did not use the word “empiricism,” and did not see themselves as united in one epistemological school or tradition. The concept of an empiricist tradition began to figure prominently in English-language philosophy only in the late 19^th century, especially in connection with arguments over the then-fledgling science of psychology. As it was then conceived, "empiricism" was the view that philosophy should begin with a picture of the mind drawn from empirical research. Locke, Berkeley, and Hume were portrayed as pioneers of this empirical approach. In the 20th century though, the very idea of an empiricist tradition shifted in meaning as people like A. J. Ayer sought to incorporate an anti-psychologistic bent. For Ayer, empiricists—indeed, philosophers—make no empirical claims at all, and so a philosophical result can never be contradicted by a result in the sciences (especially in psychology), even in principle. Instead, philosophy is concerned with choosing the most convenient linguistic frameworks for talking about the mind and the world. 

In the present paper I defend the older conception of empiricism (which I call "old-school empiricism") against the newer. My strategy is to uncover an old-school criticism of Berkeley that new-school empiricists cannot even accept as philosophically relevant. The criticism, due to the 19th century polymath Francis Galton, focuses on Berkeley's famous claim that we can frame no abstract general ideas (viz, no mental image of a generic triangle or generic human face or whatever). Galton  devised a way to produce what he called "composite portraits"—single images formed by combining dozens of images of human faces onto one photographic plate. The result, Galton held, is a pictorial representation of an "average" face. According to Galton, an idea we form when we look at such an image constitutes a counter-example to Berkeley's claim that there can be no abstract general ideas. In my view, Galton's argument is only partly successful. But even this partial success is interesting because it demonstrates the implausibility of the new-school empiricist claim that empirical results are irrelevant to philosophical argument.

ABSTRACT.  My recent essay in Philosophical Topics ("Divide et Impera!"--see above), argues for a kinship between the tradition of logical positivism that Michael Friedman has been working to revive and the strand of pragmatism that grew out of William James's early work in psychology. In particular, both traditions think a priori presuppositions play an ineliminable role in science. But the present essay draws some distinctions between those two traditions. While positivists focus on presuppositions that are meaning-constitutive of properly empirical statements in a scientific theory, I argue that Jamesean presuppositions are constitutive of the actual practice of scientific research, in the following sense. The presuppositions must be in place in order for it to be possible to garner the time, money, and reputation that is practically necessary for conducting empirical research.