Masoud Zia Ali Nasab Pour
Abstract
There is a famous idea in modal epistemology according to which conceivability of a proposition is a good guide for its possibility. Yablo (1993) persents a model for justification of modal beliefs, based on which Conceivability of a proposition is evidence for its possibility. Van Inwagen (1998) believes ...
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There is a famous idea in modal epistemology according to which conceivability of a proposition is a good guide for its possibility. Yablo (1993) persents a model for justification of modal beliefs, based on which Conceivability of a proposition is evidence for its possibility. Van Inwagen (1998) believes that if we accept Yablo’s model, we have to accept modal skepticism. To argue for this, Van Inwagen examines the modal status of the proposition that transparent iron exists on Yablo’s model. Van Inwagen claims that this proposition is undecidable on Yablo’s model. So we cannot have a justified belief that it is possible that transparent iron exists. If van Inwagen’s claim about the modal status of the proposition that transparent iron exists is correct, Yablo’s model, one might think, faces a serious problem. For if we generalize van Inwagen’s analysis of the proposition that transparent iron exists, we have to count intuitively possible propositions, propositions the modal status of which can be intuitively known as possible, as undecidable. But it is quite plausible that our beliefs about the possibility of some intuitively possible propositions are justified, so these propositions are not undecidable. I will, however, argue that van Inwagen’s analysis of modal status of the proposition that transparent iron exists cannot be generalized to all (or most) intuitively possible propositions. And therefore it is possible to accept at the same time both Yablo’s justification model and van Inwagen’s analysis about the modal status of propositions like transparent iron exist.
mohammad ali hijjati; morteza mozgi nejhad
Abstract
Intelligent systems are designed on the model of the operation of mind; but they come across, at least, the following problems: (a) Can IS solve every problem? (b) Is there any correspondence between the above problem and the undecidability of the first order predicate logic? Before finding proper answers, ...
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Intelligent systems are designed on the model of the operation of mind; but they come across, at least, the following problems: (a) Can IS solve every problem? (b) Is there any correspondence between the above problem and the undecidability of the first order predicate logic? Before finding proper answers, we should know the characteristics of an intelligent system and how it solves a problem and what do we mean by its decidability. In this article we have dealt with the above issues and will show that an intelligent system is a kind of algorithmic system and since we can find a problem (halting problem) which is unalgorithmic, that system cannot solve it; this means that an intelligent system cannot solve all the problems and hence is undecidable. This undecidability, in turn, shows that the logic (i.e. first order predicate logic) which governs the system is also undecidable.
