Criteria of Being Natural Kind and Their Relation to the Essence

The problem of natural kind is considered to be a complicated problem in philosophy as it is linked to the problem of essence on the one hand and the problem of individuals on the other. While nominalists refuse to accept universals in their ontology, realists believe in natural kinds and endeavor to justify classification of things by appealing to existence of natural kinds and their essential properties. In the first part of this paper we briefly survey two kinds of criteria for being a natural kind. In the second part we will evaluated the proposed criteria. Finally we conclude by the following six criteria: Reality and absoluteness, possessing of full essence, hierarchy, changelessness, categorization and contribution to identical theory.