Samir Okasha

Much of biological and economic theorizing takes place by modeling, the indirect study of real-world phenomena by the construction and examination of models. Books and articles about biological and economic theory are often books and articles about models, many of which are highly idealized and chosen for their explanatory power and analytical convenience rather than for their fit with known data sets. Philosophers of science have recognized these facts and have developed literatures about the nature of models, modeling, idealization, as well as testing of models and explanation by models, for both biology and economics. The impetus for this special issue came from our recognition that there is remarkably little overlap between the “modeling in biology” and “modeling in economics” literatures, despite many of the same themes appearing in these literatures.

The idea that clades might be units of selection, defended by a number of biologists and philosophers of biology, is critically examined. I argue that only entities which reproduce, i.e. leave offspring, can be units of selection, and that a necessary condition of reproduction is that the offspring entity be able, in principle, to outlive its parental entity. Given that clades are monophlyetic by definition, it follows that clades do not reproduce, so it makes no sense to talk about a clade's fitness, so clade selection is impossible. Three possible responses to this argument are examined and found wanting.

Many philosophers argue that Bayesian epistemology cannot help us with the traditional Humean problem of induction. I argue that this view is partially but not wholly correct. It is true that Bayesianism does not solve Hume’s problem, in the way that the classical and logical theories of probability aimed to do. However I argue that in one important respect, Hume’s sceptical challenge cannot simply be transposed to a probabilistic context, where beliefs come in degrees, rather than being a yes/no matter.

The problem of how to make optimal choices in the face of risk arises in both economics/decision theory and also evolutionary biology; in the former, ‘optimal’ means utility maximizing, while in the latter it means fitness maximizing. This article explores the links, thematic and formal, between the economic and evolutionary theories of optimal choice in risky situations, with particular reference to the relationship between utility and fitness. It is argued that the link is strongest between evolution and ‘nonexpected’ utility theory, rather than traditional expected utility theory.

This paper critically examines Jerry Fodor's latest attacks on evolutionary psychology. Contra Leda Cosmides and John Tooby, Fodor argues (i) there is no reason to think that human cognition is a Darwinian adaptation in the first place, and (ii) there is no valid inference from adaptationism about the mind to massive modularity. However, Fodor maintains (iii) that there is a valid inference in the converse direction, from modularity to adaptationism, but (iv) that the language module is an exception to the validity of this inference. I explore Fodor's arguments for each of these claims, and the interrelations between them. I argue that Fodor is incorrect on point (i), correct on point (ii), partially correct on point (iii), and incorrect on point (iv). Overall, his critique fails to show that adopting a broadly Darwinian approach to cognition is intellectually indefensible.

The group selection controversy is about whether natural selection ever operates at the level of groups, rather than at the level of individual organisms. Traditionally, group selection has been invoked to explain the existence of altruistic behaviour in nature. However, most contemporary evolutionary biologists are highly sceptical of the hypothesis of group selection, which they regard as biologically implausible and not needed to explain the evolution of altruism anyway. But in their recent book, Elliot Sober and David Sloan Wilson [1998] argue that the widespread opposition to group selection is founded on conceptual confusion. The theories that have been propounded as alternatives to group selection are actually group selection in disguise, they maintain. I examine their arguments for this claim, and John Maynard Smith's arguments against it. I argue that Sober and Wilson arrive at a correct position by faulty reasoning. In the final section, I examine the issue of how to apply the principle of natural selection at different levels of the biological hierarchy, which underlies the dispute between Sober and Wilson and Maynard Smith.

Marc Lange has criticized my assertion that relative to a Bayesian conception of inductive reasoning, Hume's argument for inductive scepticism cannot be run. I reply that the way in which Lange suggests one should run the Humean argument in a Bayesian framework ignores the fact that in Bayesian models of learning from experience, the domain of an agent's probability measure is exogenously determined. I also show that Lange is incorrect to equate probability distributions which 'support inductive inferences' with probability distributions which assign probability to contingent propositions/events

The levels of selection problem was central to Maynard Smith’s work throughout his career. This paper traces Maynard Smith’s views on the levels of selection, from his objections to group selection in the 1960s to his concern with the major evolutionary transitions in the 1990s. The relations between Maynard Smith’s position and those of Hamilton and G.C. Williams are explored, as is Maynard Smith’s dislike of the Price equation approach to multi-level selection. Maynard Smith’s account of the ‘core Darwinian principles’ is discussed, as is his debate with Sober and Wilson (1998) over the status of trait-group models, and his attitude to the currently fashionable concept of pluralism about the levels of selection.