【作者】 刘飞；

【导师】 李振江； 郭桥；

【作者基本信息】 河南大学 ， 逻辑学， 2011， 硕士

【摘要】 经典逻辑的推理形式是演绎的、单调的,一般被称为单调推理。它在解决基础理论问题时发挥了精确性与严格性等特点。但是在处理日常复杂语境下的推理问题时,基于经典逻辑的单调推理具有一定的局限性。与之相反,非单调推理具有一定的灵活性。其特点是推理结论具有暂时性。随着新情况的出现,结论可能会被更正,以便符合实际情况。单调推理与非单调推理之间的区别类似于弗雷格所提出的显微镜与眼睛在功能上的比较。即显微镜发挥了精确性的特点,有助于研究微观世界,但不具有眼睛在生活中的灵活性。然而,眼睛也不可能直接观察到只有通过显微镜才能看到的微观世界。非单调这一概念于上世纪70年代被提出来。经过学者们数十年对非单调推理的研究,逐渐形成了与单调的经典逻辑不同的非单调逻辑。两者之间最明显的差别是,单调逻辑的定理集随前提集的增加而单调递增,而非单调逻辑的定理集是随前提集的增加而非单调递增。具体来说,在日常语境下,以已有知识和新加入的知识为前提,可以得出新结论。新结论往往会面临两种情况:要么是与已有知识无矛盾,要么是与已有知识发生矛盾。第一种情况符合单调逻辑的特点。第二种情况符合非单调逻辑的特点。对于第二种情况,如果能确保新结论符合一般事实,那么就要对已有知识做修改。从而更新知识。对已有知识不断修改,发展新知识的过程,符合人类认识世界的一般规律。一方面,非单调推理对于理解人类如何认识世界有重要启发意义。另一方面,非单调推理也可以作为一种实用的推理工具,应用于其他学科的研究中。因此,研究非单调推理具有重要意义。研究非单调推理首先需要研究非单调逻辑系统。从逻辑学的角度,研究非单调逻辑系统的一致性与完全性等性质,可以阐明非单调推理是如何满足对推理合理性的要求。到目前为止,讨论最多的非单调逻辑系统是模态非单调逻辑和缺省逻辑等等。通过探讨这两类逻辑系统,可以深入了解模态非单调推理与缺省推理。在正文中,首先要全面了解非单调推理。通过讨论模态非单调逻辑和缺省逻辑这两种非单调逻辑系统,对非单调推理有一个整体性的认识。其次对单调推理和非单调推理之间的联系与区别有一个清楚的认识。在此基础上,深入探讨非单调推理在解决常识推理问题方面的效用和在其他学科上所具有的理论价值。更多还原

【Abstract】 The inferential form of classical logic is deductive and monotonic, and it is generally named monotonic reasoning. In solving the issues of basic theories it is accurate and strict, but there are some limitations when it is used to solve the problems of daily complex reasoning. In contrast, nonmonotonic reasoning has certain flexibility and its reasoning conclusion is temporary. When new conditions appear, the conclusions will be corrected in order to comply with the fact. The difference between monotonic reasoning and nonmonotonic reasoning is similar to the comparison proposed by Frege---the comparison between microscope and eyes on the function. Namely, microscope is characteristic of its accuracy and it is helpful to study the micro world but doesn’t have the flexibility of eyes in daily life. However, eyes couldn’t directly observe the microscopic world which could be observed only through a microscope.The concept non-monotonic reasoning was put forward in 1970s. After years of study, nonmonotonic logic has been gradually formed which is different from classical monotonic logic. The most obvious different is nonmonotonic theorem increases, with the increasing of the prerequisite of the set. Specifically, in daily context, people could draw new conclusions on the premise of existing knowledge and newly-added knowledge. Usually, new conclusions will face two kinds of situations: they are either in contradiction with existing knowledge or not. The first situation accords with the characteristic of monontonic logic and its second accords with nonmonotonic logic. For the second situation, if we could ensure that new conclusion accords with general facts. Then, we have to make changes to the existing knowledge, thus to develop new knowledge. This process of modifying existing knowledge and developing new knowledge accords with the general rule of knowing the world. On the one hand, nonmonotonic reasoning has important enlightening significance to understand the way to know the world; on the other hand, as a useful reasoning method, it could be applied to the study of other scientific fields. So it is of a great importance to study nonmonotonic reasoning.To study nonmonotonic reasoning, we must firstly study nonmonotonic logical systems. From the point of logic, through the study of consistency and completeness of nonmonotonic logical systems, we could prove that nonmonotonic reasoning can satisfy the legitimacy in daily reasoning. So far, the most often discussed systems are modal nonmonotonic logic and default logic. Through discussing the two logical systems, we could deeply understand the modal nonmonotonic reasoning and default reasoning. In the context, first of all, we should have a whole view about the nonmonotonic reasoning through the discussion of two of its systems--modal nonmonotonic logic and default logic. And then, we should have a clear understanding about the relation and distinction between monotonic reasoning and nonmonotonic reasoning. On this basis, we explore its utility in common sense reasoning and its theoretical value in other subjects.更多还原