Modal Logic And Essentialism

This dissertation firstly gives a survey of contemporary modal logic, so that it constructs a technical platform for the following discussion. Next, through discussing three main kinds of philosophical problems of modal logic, the dissertation holds that essentialism is central to the philosophical problems of modal logic. Accordingly, the dissertation discusses essentialism problems of modal logic in two main aspects, i.e. doctrine of possible worlds and scheme of essentialism.The dissertation holds that possible worlds doctrines of extreme realism and extreme nominalism are both mistaken, and that the really feasible one should be moderate realism. From this, the dissertation constructs a scheme of moderate modal realism: possible world is a way of co-existence of all the things, it is a sort of objective reality, its reality does not depend on human's subjective consciousness, and it is not an artificial stipulation. Possible world is reality adhering to objective things, thus its objectivity origins from objective things. Being a sort of objective reality, possible word is prior to attribute, relation and other adhering reality, and it is not a kind of construction or definition of facts or state of affairs. Because of conceptual priority, there is no possibility of circularity in demonstrating possible worlds. In addition, for the special ontological status of possible worlds, there is no problem of distinguishing between possible worlds and impossible worlds. As to the problem of invalidity of the principle of indiscernibility of identicals, the dissertation holds that it is purely fictitious, for the use of Leibniz's law is confined to the interior of possible worlds. And the so-called violation of the principle of identicals of indiscernibility and transitivity of identity is because essential attributes and non-essential attributes are not differentiated. The dissertation holds that the moderate modal realism need be supplemented by a feasible scheme of essentialism.Through inspecting the essentialism thoughts of Aristotle, analyzing and making use of the expositions of some other philosophers, the dissertation suggests the formal characterization of Aristotelian essentialism and points out that modal logic is committed to essentialism in the following sense, i.e. approving of the meaningfulness of essentialism sentences. The dissertation holds that natural kind has its essence indeed, that is, the internal structure all its members share, supports the above opinion of Kripke and Putnam, and gives a strong justification for it. On the problem of individual essence, the dissertation suggests a brand-new scheme for organism, i.e. the doctrine of origin and gene. The dissertation holds that although individual origin meets the necessary condition of being individual essence, the known relevant demonstrations are mistaken. Therefore, the dissertation designs another strategy to justify it, i.e. reductio ad absurdum. However, the dissertation points out at the same time that individual origin does not meet the sufficient condition of being individual essence, and this is because variations of genetic code cause different organisms borne. By proper revision and supplement for the doctrine of individual...