This paper argues that there are powerful similarities between cognitive development in children and scientific theory change. These similarities are best explained by postulating an underlying abstract set of rules and representations that underwrite both types of cognitive abilities. In fact, science may be successful largely because it exploits powerful and flexible cognitive devices that were designed by evolution to facilitate learning in young children. Both science and cognitive development involve abstract, coherent systems of entities and rules, theories. In both cases, theories provide predictions, explanations, and interpretations. In both, theories change in characteristic ways in response to counterevidence. These ideas are illustrated by an account of children's developing understanding of the mind.

While endorsing Gopnik's proposal that studies of the emergence and modification of scientific theories and studies of cognitive development in children are mutually illuminating, we offer a different picture of the beginning points of cognitive development from Gopnik's picture of “theories all the way down.” Human infants are endowed with several distinct core systems of knowledge which are theory-like in some, but not all, important ways. The existence of these core systems of knowledge has implications for the joint research program between philosophers and psychologists that Gopnik advocates and we endorse. A few lessons already gained from this program of research are sketched.

Child's play? Certainly Alison Gopnik is in good company in pointing to connections between science and child development. To mention just a few luminaries: in psychology, Freud (followed by Erikson and Piaget) looked at the developmental connection between children's play and adult work; in philosophy, Thomas Reid may have been the first to ground the faculty of reasoning in developmental stages that “unfold themselves by degrees; so that it [the child] is inspired with the various principles of common sense” (1764, V, 7). As for connecting commonsense reasoning and science, according to Einstein, “The whole of science is nothing more than a refinement of everyday thinking” (1954, 290). Quod erat demonstrandum.

My concern is with the possible implications of research in developmental psychology for understanding the workings of modern science. I agree both with Gopnik's general naturalistic orientation and with her more specific claims about scientists as cognitive agents. Neither the formal structure of propositions nor the social structure of scientific communities provides sufficient resources for the understanding we seek. So I agree that the empirical study of human cognition is not only relevant, but necessary, for understanding how science works (Giere 1988, 1989).

Although most philosophers are not aware of it, research in cognitive development and in learning in the last decade has made considerable use of the characterizations of the nature and development of scientific knowledge proffered by philosophers of science. In a “reflexive” move, Alison Gopnik proposes philosophers of science can profit from the research of psychologists investigating cognitive development-specifically from that group of researchers who advocate the “theory theory.”

Once upon a time in evolutionary theory, everything happened for the best. Predators killed only the old or the sick. Pecking orders and other dominance hierarchies minimized wasteful conflict within the group. Male displays ensured that only the best and the fittest had mates. In the culmination of this tradition, Wynne-Edwards (1962, 1986) argued that many species have mechanisms that ensure groups do not over-exploit their resource base. The “central function” of territoriality in birds and other higher animals is “of limiting the numbers of occupants per unit area of habitat” (1986, 6). Species with dominance hierarchies, species with lekking breeding systems, and species with communal breeding regulate their populations. These social mechanisms have population regulation as their “underlying primary function” (1986, 9). Wynne-Edwards argued that these mechanisms evolve through group selection. Populations without such mechanisms are apt to go extinct by eroding their own resource base.

In a reply to Nicholas Maxwell, Stein has proved that Minkowski spacetime can leave room for the kind of indeterminateness required both by certain interpretations of quantum mechanics and by objective becoming. By examining the consequences of outcome dependence in Bell-type experiments for the co-determinateness of spacelike-related events, I argue that the only becoming relation that is compatible with both causal and noncausal readings of the quantum correlations is the universal relation. This result might also undermine interpretations of quantum mechanics requiring non-epistemically indeterminate states before measurement and hyperplane-dependent wave collapse.

In this paper it is suggested that Freud's ‘tally argument’ (Grünbaum 1984) is not best interpreted as a risky claim concerning the efficacy of psychoanalytic therapy, but as a risky claim concerning the implications of theoretical psychoanalytic explanations of the efficacy of psychoanalytic therapy. Despite the fact that Freud never empirically established that these implications hold, the ‘tally argument’ does draw attention to a critical distinction that is too often neglected in contemporary empirical studies of psychoanalysis and other forms of psychotherapy: between empirical evaluations of the efficacy of psychotherapy and empirical evaluations of theoretical explanations of the efficacy of psychotherapy, and the different forms of comparative enquiry relevant to each. It is argued that the contemporary neglect of this critical distinction, in conjunction with the common negative conception of placebo control treatments in psychotherapy research, has led to the epistemic impoverishment of experimental studies of the various professional psychotherapies. In consequence, although there is good empirical evidence for the efficacy of psychoanalysis and other forms of professional psychotherapy, there is no good empirical evidence for theoretical psychoanalytic explanations of the efficacy of psychoanalysis, or for traditional theoretical explanations of the efficacy of other forms of professional psychotherapy.

Using Grünbaum 1984 and 1993 as a springboard, Greenwood (this issue) claims to have offered several methodologically salubrious and exegetically illuminating theses on empirical evaluations of theoretical explanations of psychotherapeutic efficacy. According to his exegesis of Grünbaum's construction (1984, Ch. 2, Section C; 1993, 184–204) of Freud's “Tally Argument,” that argument bespeaks a rife neglect of the epistemologically-significant distinction between empirical evaluations of the efficacy of psychotherapy and evaluations of theoretical explanations of that efficacy. Greenwood presents a defense of a qualified version of Popper's critique of psychoanalysis against Grünbaum's objections to it (1984, Ch. 1B). Finally, Greenwood offers a clarification of the concept of a “placebo control” investigation, taking issue with Grünbaum's 1993 (84–87, 91–93).

In the present paper, it is argued contra Greenwood that: (1) his purportedly “best” reading of Freud's Tally Argument and of its import founders, (2) the distinction that Greenwood bemoans as being neglected by mental health researchers actually is a commonplace in the literature on treatment-process and therapeutic outcome, (3) Greenwood's defense of Popper's critique of psychoanalysis is an anachronism, and (4) Greenwood's conceptual analysis of placebo controls is nebulous and misconceived.

John Greenwood (this issue) claims that neglect of an important methodological distinction has contributed directly to the “epistemic impoverishment” of empirical studies of all forms of professional psychotherapy. I challenge this claim, as well as other important claims he makes about the efficacy of psychoanalysis and other forms of psychotherapy.

In a recent article, Wayne (1995) offers a critique of Horwich's (1982) Bayesian explication of the confirmational significance of evidential diversity. Presently, I argue that Wayne's reconstruction of Horwich's account is not faithful to Horwich's original presentation. Because Wayne's reconstruction is uncharitable, his criticisms turn out to be off the mark. I try to provide a more faithful and charitable rendition of Horwich's account. Unfortunately, even this more charitable reconstruction of Horwich's position seems—at best—to provide an incomplete explication of the confirmational significance of evidential diversity.

Andrew Wayne (1995) discusses some recent attempts to account, within a Bayesian framework, for the “common methodological adage” that “diverse evidence better confirms a hypothesis than does the same amount of similar evidence” (112). One of the approaches considered by Wayne is that suggested by Howson and Urbach (1989/1993) and dubbed the “correlation approach” by Wayne. This approach is, indeed, incomplete, in that it neglects the role of the hypothesis under consideration in determining what diversity in a body of evidence is relevant diversity. In this paper, it is shown how this gap can be filled, resulting in a more satisfactory account of the evidential role of diversity of evidence. In addition, it is argued that Wayne's criticism of the correlation approach does not indicate a serious flaw in the approach.

In a recent essay (1995), Andrew Wayne charges that Bayesian attempts to account for the rule that, ceteris paribus, diverse evidence confirms better than narrow evidence are inadequate. I reply to these criticisms and argue that, on the contrary, one of the Bayesian approaches considered by Wayne does an excellent job of explaining why, and under what circumstances, diverse evidence is valuable.