Naturalness of Kinds and the Rules of Nature

Scientific disciplines divide the particulars they study into kinds and theorize about them, but it is difficult to determine the necessary and sufficient conditions for a particular to be classified under a certain kind.What is a natural kind? Scientists normally assume that in the process of studding the nature they discover some real independent kinds; not that they invent them subjectively. Are they true? If natural kinds really exist and they are distinguishable from non-natural kinds, then what is the standard of this distinction? In this paper we first go through natural kinds and their related issues. Then, while explaining the difference between naturalism and Conventionalism, we offer a description of the causal theory of reference and its suggested solutions for distinguishing natural from non-natural. Finally we show that the difference between naturalism and conventionalism can be more accurately explained through the rule of the "explanatory value".