In this study, the basic arguments of Thomas Aquinas, who was the first philosopher to have systematized on the logical platform the tradition of the natural law theory that has reached today from Ancient Greece and has a deep-rooted philosophical-historical background, on this issue will be addressed and then the approach of the philosopher will be discussed critically. Saint Thomas is the most important philosopher of the classical natural law tradition since he maintained the tradition of natural law in Ancient Greece and Rome in some aspects and he represented an intellectual point breaking from a longstanding tradition that continued up until his time in some other aspects. This continuity and break in question influenced the discussions in the modern natural law theory to a great extent. Therefore, it is possible to suggest that the natural law doctrine of the philosopher played an important part in shaping of the modern natural law theory. Two key characteristics come to the fore in Saint Thomas’ natural law doctrine. The first characteristic is related to the fact that natural law becomes one of the aspects of Divine providence. The second characteristic is related to the fact that the natural law doctrine provides a framework that constructs the principles of practical rationality giving the criteria for actions of human being. In the article, the basic arguments regarding these characteristics will be respectively explained and the link between eternal law and natural law, natural law and human law will be demonstrated in terms of the arguments in question. Then the counter-arguments that might be put forward regarding Saint Thomas’ doctrine judicially, philosophically (both in the metaphysical and moral contexts) and politically will be presented.