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Imperative logic is the field of logic concerned with arguments containing sentences in the imperative mood. In contrast to sentences in the declarative mood, imperatives are neither true nor false. This leads to a number of logical dilemmas, puzzles, and paradoxes. Unlike classical logic, there is almost no consensus on any aspect of imperative logic. ==Jørgensen's Dilemma== One of a logic's principal concerns is logical validity. It seems that arguments with imperatives can be valid. Consider: :P1. Take all the books off the table! :P2. ''Foundations of Arithmetic'' is on the table. :C1. Therefore, take ''Foundations of Arithmetic'' off the table! However, an argument is valid if the conclusion follows from the premises. This means the premises give us reason to believe the conclusion, or, alternatively, the truth of the premises determines truth of the conclusion. Since imperatives are neither true nor false and since they are not proper objects of belief, none of the standard accounts of logical validity apply to arguments containing imperatives. Here is the dilemma. Either arguments containing imperatives can be valid or not. On the one hand, if such arguments can be valid, we need a new or expanded account of logical validity and the concomitant details. Providing such an account has proved challenging. On the other hand, if such arguments cannot be valid (either because such arguments are all invalid or because validity is not a notion that applies to imperatives), then our logical intuitions regarding the above argument (and others similar to it) are mistaken. Since either answer seems problematic, this has come to be known as Jorgensen's dilemma, named after Jørgen Jørgensen (da). While this problem was first noted in a footnote by Frege, it received a more developed formulation by Jørgensen.〔Frege, G. (1892) 'On sense and reference', in Geach and Black (eds.) Translations from the Philosophical Writings of Gottlob Frege Oxford: Blackwell.〕〔Jørgensen, J. (1938) 'Imperatives and logic', ''Erkenntnis'' 7: 288-98.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Imperative logic」の詳細全文を読む スポンサード リンク
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