On the Concept of Quantum State Reduction: Inconsistency of the Orthodox View

The argument is re-examined that the program of deriving the rule of state reduction from the Schroedinger equation holding for the object-apparatus composite system falls into a vicious circle or an infinite regress called the von Neumann chain. It is shown that this argument suffers from a serious physical inconsistency concerning the causality between the reading of the outcome and the state reduction. A consistent argument which accomplishes the above program without falling into the circular argument is presented.Comment: 15 pages, LaTeX, 1 Postscript figur

Belief Revision with Uncertain Inputs in the Possibilistic Setting

This paper discusses belief revision under uncertain inputs in the framework of possibility theory. Revision can be based on two possible definitions of the conditioning operation, one based on min operator which requires a purely ordinal scale only, and another based on product, for which a richer structure is needed, and which is a particular case of Dempster's rule of conditioning. Besides, revision under uncertain inputs can be understood in two different ways depending on whether the input is viewed, or not, as a constraint to enforce. Moreover, it is shown that M.A. Williams' transmutations, originally defined in the setting of Spohn's functions, can be captured in this framework, as well as Boutilier's natural revision.Comment: Appears in Proceedings of the Twelfth Conference on Uncertainty in Artificial Intelligence (UAI1996

The Historical Perspective of the Problem of Interpersonal Comparisons of Utility

The starting-point of the article is the inconsistency between the established practice of acceptance in many cases, of economic policy (i.e. progressive taxation, national insurance policies) and the theoretical rejection of interpersonal comparisons of utility who see it as an unscientific value judgement. The inconsistency is explained by identifying three groups of theorists: (1) those who thought of comparability as a value judgement and unacceptable for economic policy considerations (positivists), (2) those who agreed with the positivists, on the normative nature of comparability but accepted it as a basis for economic policy, and (3) those who thought of it as part of a scientific economics. The implication was that, despite the dominance of positivist methodology in other sub-fields, the historical experience points to the difficulty of applying positivist methodology to the issue of comparability. If the inconsistency is thus due to the inappropriateness of the positivist approach, the only possible solution is the explicit abandonment of this approach at least in matters related to the collective aspects of economics.History of Economics; Welfare Economics

Modelling change in individual characteristics: an axiomatic framework

Economic models describe individuals in terms of underlying characteristics, such as taste for some good, sympathy level for another player, time discount rate, risk attitude, and so on. In real life, such characteristics change through experiences: taste for Mozart changes through listening to it, sympathy for another player through observing his moves, and so on. Models typically ignore change, not just for simplicity but also because it is unclear how to incorporate change. I introduce a general axiomatic framework for defining, analysing and comparing rival models of change. I show that seemingly basic postulates on modelling change together have strong implications, like irrelevance of the order in which someone has his experiences and ‘linearity’ of change. This is a step towards placing the modelling of change on solid axiomatic grounds and enabling non-arbitrary incorporation of change into economic models