Malthus v. Bailey on the Measure of Value: A Lesson in "Methodological Humility"

That Malthus was guilty of egregious error in his claim to have established the labor-commanded magnitude as an "invariable" unit of value is well-known. Even his modern biographer could appeal only to a "kink or a crotchet, some kind of cerebral block" to excuse Malthus's persistent failure to recognize the manifestly tautological character of his position. Yet the familiar form of Malthus's argument, as it appeared in his later work, differed in several respects from its earliest statement in the first edition of his Principles. In this essay we trace out the several changes made to Malthus's argument, often in response to his many critics; and we find in the midst of those alterations a common characteristic that serves to reveal the character of that "kink or crotchet": an obsession with mathematical operations producing a unit outcome. We draw two lessons from this sorry episode in our history. First, the sterility of the debate between Malthus and his critics serves to highlight the central importance of a precise and commonly understood vocabulary of scientific expression. This was, it is true, no more than a dispute over words; but as they are the vessels of our thoughts, words-of precise and commonly understood meaning-are critical to the progress of a science. Second, the heat of that debate highlights the insidious capacity of practitioners to mistake for scientific principles what are no more than "intricate series of definitions," a lesson which, when taken seriously, cannot fail but to impart a salutary "methodological humility."Labor-command; Malthus; Ricardo; Samuel Bailey

Generalized thermodynamics and kinetic equations: Boltzmann, Landau, Kramers and Smoluchowski

We propose a formal extension of thermodynamics and kinetic theories to a larger class of entropy functionals. Kinetic equations associated to Boltzmann, Fermi, Bose and Tsallis entropies are recovered as a special case. This formalism first provides a unifying description of classical and quantum kinetic theories. On the other hand, a generalized thermodynamical framework is justified to describe complex systems exhibiting anomalous diffusion. Finally, a notion of generalized thermodynamics emerges in the context of the the violent relaxation of collisionless stellar systems and two-dimensional vortices due to the existence of Casimir invariants and incomplete relaxation. A thermodynamical analogy can also be developed to analyze the nonlinear dynamical stability of stationary solutions of the Vlasov and 2D Euler-Poisson systems. On general grounds, we suggest that generalized entropies arise due to the existence of ``hidden constraints'' that modify the form of entropy that we would naively expect. Generalized kinetic equations are therefore ``effective'' equations that are introduced heuristically to describe complex systems

PHI : a logic-based tool for intelligent help systems

We introduce a system which improves the performance of intelligent help systems by supplying them with plan generation and plan recognition components. Both components work in close mutual cooperation. We demonstrate two modes of cross-talk between them, one where plan recognition is done on the basis of abstract plans provided by the planner and the other where optimal plans are generated based on recognition results. The examples which are presented are taken from an operating system domain, namely from the UNIX mail domain. Our system is completely logic-based. Relying on a common logical framework--the interval-based modal temporal logic LLP which we have developed--both components are implemented as special purpose inference procedures. Plan generation from first and second principles is provided and carried out deductively, whereas plan recognition follows a new abductive approach for modal logics. The plan recognizer is additionally supplied with a probabilistic reasoner as a means to adjust the help provided for user-specific characteristics