The Chances of Explanation: Causal Explanation in the Social, Medical, and Physical Sciences Paul Humphreys, 1989 Princeton University Press x+170 pp., £12.95 (paperback) ISBN 0 691 020286 8; £25.00 (hardback) ISBN 0 69107353 8In Search of a Better World: Lectures and Essays from Thirty Years Karl Popper London, Routledge £25.00 (hardback)Artificial Morality: Virtuous Robots for Virtual Games Peter Danielson, 1992 London, Routledge £35.00 (hardback) ISBN 0 415 034841; £10.99 (paperback) ISBN 0 415 07691 9A System of Pragmatic Idealism Nicholas Rescher, (...) 1992 Princeton, Princeton University Press 335pp., $37.50 (hardback). (shrink)

InMorals by Agreement, David Gauthier (1986) argues that it is rational to intend to cooperate, even in single-play Prisoner's Dilemma games, provided (1) your co-player has a similar intention; (2) both intentions can be revealed to the other player. To this thesis four objections are made. (a) In a strategic decision the parameters on which the argument relies cannot be supposed to be given. (b) Of each pair ofa-symmetric intentions at least one is not rational. But it is impossible to (...) form symmetric intentions to cooperate conditionally. For the condition on which the decision depends cannot be fulfilled without deciding. (c) If one's intention has to be ascertained on the basis of information about one's past performance, it is straightforwardly rational to intend to cooperate, but there is no reason to do so in a single-play PD. (d) The argument cannot be extended ton-person games which are Gauthier's principal concern. (shrink)