Abstract

Abstract: Logical theory traditionally assumes the following: (1) Logical inference is a relation between sentences (or propositions), not between thoughts (or anything cognitive). (2) The validity of an argument is only dependent on the logical structure of the sentences and independent of their meaning. In practical reasoning, however, these assumptions are not valid. In this paper I want to show that by taking expectations into account, one can achieve a much better understanding of how logic is put to work by humans. In particular, one obtains a very simple analysis of nonmonotonic reasoning. I will also discuss the cognitive origins of expectations. Then a man said: Speak to us of Expectations. He then said: If a man does not see or hear the waters of the Jordan, then he should not taste the pomegranate or ply his wares in an open market. If a man would not labour in the salt and rock quarries, then he should not accept of the Earth that which he refuses to give of himself. Such a man would expect a pear of a peach tree. Such a man would expect a stone to lay an egg.

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