It is argued that the natural and human vicissitudes of the Northern Hemisphere—or at least western European history between 1315 and 1648—provide a preview of the sort of consequences for humanity and its demography that will result from the serious if not catastrophic climate change that is now anticipated by the Intergovernmental Panel on Climate Change (IPCC). Game theory suggests that at least some nation-state players in the strategic problem that climate change raises will not choose Nash equilibria that mitigate the problem. The only feasible solution will be the discovery or invention of some non-greenhouse-gas-emitting energy source so cheap that its owner will be indifferent to free-riding by all other users of energy. Recent efforts to develop fusion reactors do not provide much hope for this eventuality.

The essay agues that there is little scope for ideal theory in politicalphilosophy, even under Rawls’s conception of its aims. It begins byidentifying features of a standard example of ideal theory in physics— the ideal gas law, PV=NRT and draws attention to thelack of these features in Rawls’s derivation of the principles ofjustice from the original position. A. John Simmons’s defense ofideal theory against criticisms of Amartya Sen is examined, as are furthercriticisms of both by David Schmidtz. The essay goes on to develop a conceptionof the domain of social relations to be characterized by justice that suggeststhat as a moving target it makes ideal theory otiose. Examination ofRawls’s later views substantiate the conclusion that ideal theory aspropounded in A Theory of Justice is a mistaken starting point in the enterpriseof political philosophy. Differences between the domains of ideal theory inmathematics, physics, and economics on the one hand, and political philosophy onthe other, reinforce this conclusion.

In this paper I bring together and discuss claims that David Lewis has made in Counterfactuals, and in “Causation,” and explore a number of difficulties which the views of these two works make for each other. If these difficulties are as serious as I suggest, they will require revision or rejection of the view of causation that Lewis defends.

Scientific realism at least in large measure reflects the conviction that physics limns the true nature of reality; that it is the right metaphysical picture of things. This conviction is in turn a product of the failure of positivism's attempt to expunge metaphysics from the corpus of philosophically respectable activities. Since natural science is objective knowledge of the world par excellence post-positivists have embraced it as the ontology which their predecessors had failed to make unnecessary. Scientific realism is metaphysics, shameless or unashamed.

The turtle's optokinetic response is described by a simple model that incorporates visual-response properties of neurons in the pretectum and accessory optic system. Using data from neuronal and eye-movement recordings that have been previously published, the model was realized using algebraic-block simulation software. It was found that the optokinetic response, modelled as a simple negative feedback system, was similar to that measured from a behaving animal. Because the responses of retinal-slip detecting neurons corresponded to the nonlinear, closed-loop optokinetic response, it was concluded that the visual signals encoded in these neurons could provide sufficient sensory information to drive the optokinetic reflex. Furthermore, it appears that the low gain of optokinetic eye movements in turtles, which have a negligible velocity storage time constant, may allow stable oculomotor output in spite of neuronal delays in the reflex pathway. This model illustrates how visual neurons in the pretectum and accessory optic system can contribute to visually guided eye movements.

The F-twist is giving way to the methodology of scientific research programs. Milton Friedman's “Methodology for Economics” is being supplanted as the orthodox rationale for neoclassical economics by Imre Lakatos' account of scientific respectability. Friedman's instrumentalist thesis that theories are to be judged by the confirmation of their consequences and not the realism of their assumptions has long been widely endorsed by economists, under Paul Samuelson's catchy rubric “the F-twist.” It retains its popularity among economists who want no truck with methodology, but among the increasing number of able economists who are writing on methodology the F-twist has been surrendered, not so much because these writers have decided it is false, as because something better has finally come along.