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The Rationality of Probabilities for Actions in Decision Theory

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The Rationality of Probabilities for Actions in Decision Theory

ABSTRACT: Spohn's decision model, an advancement of Fishburn's theory, is valuable for making explicit the principle used also by other thinkers that 'any adequate quantitative decision model must not explicitly or implicitly contain any subjective probabilities for acts.' This principle is not used in the decision theories of Jeffrey or of Luce and Krantz. According to Spohn, this principle is important because it has effects on the term of action, on Newcomb's problem, and on the theory of causality and the freedom of the will. On the one hand, I will argue against Spohn with Jeffrey that the principle has to be given up. On the other, I will try to argue against Jeffrey that the decision-maker ascribes subjective probabilities to actions on the condition of the given decision situation.

Spohn's (1977, 1978) decision model, an advancement of Fishburn's theory (1964), is valuable for making explicit a principle which is used by Savage (1954/1972) and Fishburn (1964). The principle is the following: "Any adequate quantitative decision model must not explicitly or implicitly contain any subjective probabilites for acts." (1) (Spohn 1977, p. 114) This principle is not used in the decision theories of Jeffrey (1965, 1983) and of Luce and Krantz (1971). According to Spohn (1977) this principle is important, because it has implications for the concept of action, Newcomb's problem, theory of causality and freedom of will. On the one hand I will try to argue against Spohn (1977, 1978) with Jeffrey (1965, 1968, 1977, 1983) that the principle has to be given up. On the other hand I will try to argue against Jeffrey (1965, 1968, 1977, 1983) that the decision-maker ascri...

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Nozick, R. (1969), "Newcomb's Problem and Two Principles of Choice", in N. Rescher et al. (eds.), Essays in Honor of Carl G. Hempel, Reidel, Dordrecht: 114-146.

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Spohn, W. (1977), "Where Luce and Krantz Do Really Generalize Savage's Decision Model", Erkenntnis 11: 113-134.

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