One of the important controversies in the biology of the 18th century was “the diversity of different forms of organisms”. "Why did this form of living creature appear among the various forms that had the possibility of life?" was the main question. Scientists resorted to the theory of stability of types. This theory had its origins in theology, which believed that every type and form of living beings was created by God. The arguments that were expressed in this direction were usually teleological arguments, based on which the final explanation of creation, the goals and objectives of every creature and the final causes of its functioning, was considered the most justified explanation of the structure and form of a living being. George Cuvier, the famous French biologists of the 18th and 19th centuries, was among the most influential scientists who critically examined the teleological explanation of the life of a living organism by stating the " The Principle of the Conditions of Existence ". Without resorting to teleological explanations, he showed that the explanation of the life of a living being or its functions is related to a set of necessary conditions for the expression or existence of that function. In this article, first I try to show that the teleological explanation is based on the concept of "function" in biology. Secondly, I show how Cuvier presented a non-theological interpretation of the life form of a living being by stating" The Principle of the Conditions of Existence ".