As Deirdre suggests, Sidgwick was a bright boy--brighter, in fact, than Deidre probably realizes. His utilitarian approach to law is the subject of a paper that appears in the first 2007 issue of the American Law and Economics Review. When discussing the collision between individual interests in the use of natural resources, including the potential depletion of mines, fisheries, and plant species, and the diversion of waterways necessary for irrigation and "the supply of motive power," Sidgwick points out that in a "perfectly ideal community of economic men all persons concerned would doubtless voluntarily agree to take the measures required to ward off such common dangers" (Sidgwick, Principles of PE, 1901, pp. 409-10). It would be foolhardy to suggest that Sidgwick's "perfectly ideal community of economic men" is nineteenth-century-speak for a world of zero transaction costs. Nevertheless, both Coase and Sidgwick understood that, under idealized conditions, agents would cooperate to resolve these self-interest-generated problems of harmful effects. But of course, these are only idealized conditions. Sidgwick argues that the underlying conditions necessary for the system of natural liberty to work the wealth-maximizing magic so often attributed to it do not, in many instances, correspond to actual economic circumstances. The effect, he says, is that "even in a society composed-solely or mainly-of 'economic men,' the system of natural liberty would have, in certain conditions, no tendency to realize the beneficent results claimed for it" (1901, pp. 402-403). Sidgwick instances the depletion of common pool resources, where "the efforts and sacrifices of a great majority are liable to be rendered almost useless by the neglect of one or two individuals" (1901, p. 410), and he illustrates the problem by applying the then-emerging marginal analysis to the fishery: "Take, for instance, the case of certain fisheries, where it is clearly for the general interest that the fish should not be caught at certain times, or in certain places, or with certain instruments, because the increase of actual supply obtained by such captures is overbalanced by the detriment it causes to the prospective supply. Here-however clear the common interest might be-it would be palpably rash to trust to voluntary association for the observance of the required rules of abstinence; since the larger the number that voluntarily abstain, the stronger becomes the inducement offered to those who remain outside the association to pursue their fishing in the objectionable times, places, and ways, so long as they are not prevented by legal coercion" (Sidgwick, Principles of PE, 1901, p. 410). Steven G. Medema