The author's tenet is that any account of concept of law as system of rules makes no claim at ethical concepts like the concept of the good, values and aims. In fact the concept of law (in the appropriate sense) excludes all of these ethical concepts. His thesis is based on two theories - H. Hart's social rule theory of law, and J. Searle's theory of social facts - and can be summarized as follows. (1) If we accept that the rules of law and ethics are social rules, then individuals can follow rules if rules can be explained with the help of the concept of knowledge. (2) According to this, individuals can know social and collective institutions by knowing the rules and a statement can be seen as a normative one if someone accepts the survival of the society or community in question as a general aim and the content of the statement can be interpreted according to this aim. (3) This means that the rules of law and conventional ethics allow individuals to know similar institutional facts and since there are a lot of smaller and bigger communities within society, laws cannot be judged based on ethics. (4) Individuals are following the rules of law based on their knowledge of social or collective institutions and their faculty of decision. (5)However, individual knowledge depends on the rules of their smaller and bigger communities. The author's overall aim is to offer arguments for the theory of positivism of law and against the natural law theory in order to show that this kind of positivism is not impossible.