The most influential criticisms of legal positivism all stem in one way or another from the suspicion that it does not give morality the legitimacy it deserves. A theory that emphasizes the factuality of law seems to contribute little to our understanding that law has important functions in ensuring the proper functioning of human life, that the rule of law is a cherished ideal, and that the language and practice of law are highly moralized. Accordingly, critics of positivism argue that the most important features of law are not to be found in its source-based character, but in the ability of law to promote the common good, protect human rights, or govern with integrity. It is a curious fact that almost all theories that emphasize the essentially moral character of law regard the character of law as essentially good. The gravity of Fuller`s philosophy is that law is essentially a moral enterprise made possible only by a robust adherence to one`s own inner morality. The thought that the law could have an inner immorality never crossed his mind. But, as Hart acknowledged, where there is “a union of primary and secondary rules”—that is, wherever there is a right—moral hazard arises out of necessity. Not only are there new effective forms of oppression that are not available in communities with more diffuse forms of social organization, but there are also new vices: the possible alienation of community and value, the loss of transparency, the rise of a new hierarchy and the possibility that some, who should oppose injustice, be bought from property. what the legal system entails. Although law has its virtues, it also necessarily risks certain vices, which marks an inverse link between law and morality. Critics say that what many legal positivists fail to notice is that there are several reasonable natural law reasons for the positivity of the law.
Pure moral standards (“Thou shalt not kill the innocent”) are too vague and open to serve as reliable guidelines for human behavior. In order to coordinate complex human activities, the law must sink into concrete particularities: not to “drive safely”, but “to drive no more than 55 MPH”. In the abstract, “driving safely” seems to have intrinsic moral force, while “driving at 55” seems morally arbitrary. But in the context of the law, the statement “drive safely” would invite anarchy on the road and would therefore be deeply immoral, whereas setting a certain limit is morally necessary to achieve safe driving. Natural law, then, shows us why it is morally necessary for law to be largely morally indifferent in its content. Similarly, many legal positivists like Raz argue that we must be able to identify legal norms without resorting to moral arguments, because the purpose of a legal system is to provide a framework for social interaction in contexts where there is no agreement on moral principles. Again, we can see that there are good moral reasons to insist on objective criteria to determine valid legal norms if we hope to maintain a legal order that can be respected by citizens with very different moral views. In short, natural law theorists say that, in a wide range of legal norms and institutions, the requirements of a valid law identified by legal positivists are not only compatible with, but also find their deepest justification for it (Finnis 1980). But many positivists view the discretionary thesis as a contingent claim that applies to some, but not all, legal systems. Hart, for example, believes that there will inevitably be cases that do not clearly fall within a rule, but acknowledges that a recognition rule could deprive judges of the discretion to legislate in such cases by requiring judges to “decline jurisdiction or refer matters not governed by existing law to the legislature” (Hart, 1994, p. 272). Indeed, Hart`s general positivism allows him to claim that a recognition rule could compel judges to decide cases exactly as Dworkin advocates (Hart, 1994, 263; and see section IV-2 below).
At least for inclusive positivists like Hart, the discretion thesis makes a different type of assertion than the conceptual affirmations that form the theoretical core of positivism (Himma 1999). While the field has traditionally focused on explaining the nature of law, some scholars have begun to examine the nature of areas of law, such as tort liability, contract law, or criminal law. These researchers focus on what distinguishes certain areas of law and how one area differs from another. A particularly fruitful area of research has been the distinction between tort law and criminal law, which refers more generally to the difference between civil and criminal law.  The most influential criticisms of Austin`s version of the genealogical thesis, however, are due to H. L. A. Hart`s seminal work, The Concept of Law.
Hart points out that Austin`s theory provides, at best, a partial representation of legal validity because it focuses on one type of rule, namely that which requires citizens to “do or refrain from certain actions, whether they like it or not” (Hart, 1994, 81). While any legal system must contain so-called primary rules governing the behavior of citizens, Hart believes that a system consisting entirely of the kind of restrictions on liberty found in criminal law is at best a rudimentary or primitive legal system. However, positivism is sometimes more credibly associated with the idea that legal philosophy is or should be value-neutral. Kelsen, for example, says, “The function of jurisprudence is not the evaluation of its subject, but its worthless description” (1960 [1967: 68]) and Hart described his work at one point as “descriptive sociology” (1961 [2012: v]). But a description of what? “Law” is an anthropocentric subject that depends not only on our sensory incarnation, but also, as its necessary links with morality show, on our meaning and moral capacities.