However, a secular critique of the doctrine of natural law was formulated by Pierre Charron in his De la sagesse (1601): « The sign of a natural law must be the universal respect in which it is preserved, for if there were something that nature had really commanded us, we would undoubtedly obey it universally: Not only would all nations respect it, but every individual. Instead, there is nothing in the world that is not contradictory and controversial, nothing that is not rejected, not only by one nation but by many; Similarly, there is nothing strange and (by many) unnatural that is not approved in many countries and allowed by their customs. The decline of theories of natural law took place in the 18th and 19th centuries with the subsequent development of empirical study methods and scientific behavior. Theories of natural law were denounced mainly because their source was called a divine entity. The profound Austin rejected natural law on the grounds that it was ambiguous and misleading, ruthlessly criticizing the school of natural law as « mere nonsense, natural right-wing rhetorical nonsense and indescribable on stilts. » John Locke also recognized the existence of certain inalienable natural rights. He categorized them as « life, liberty, and property (property). » Locke`s social contract is based on liberalism. There is a different view of natural law. It is the consideration of positivist or empiricist views of abstract metaphysical ideals and ideas, commonly known as natural law. Examples of natural law abound, but philosophers and theologians have differed throughout history in their interpretations of this doctrine. Theoretically, the commandments of natural law should be constant over time and throughout the world, because natural law is based on human nature, not culture or customs. The United States Declaration of Independence declares that it has become necessary for the people of the United States « to occupy the separate and equal position to which the laws of nature and the God of nature entitle them. » Some of the early American jurists and judges viewed natural law as too weak, amorphous, and transitory a legal basis for establishing concrete rights and government restrictions.
 However, natural law has served as the authority for claims and legal rights in some judicial decisions, legislative acts, and legal decisions.  Robert Lowry Clinton argues that the Constitution of the United States is based on common law and that the common law is based on classical natural law.  Ronald Dworkin`s so-called third theory of law is best understood as a response to legal positivism, which is essentially composed of three theoretical obligations: the social fact thesis, the conventionality thesis, and the separability thesis. The social fact thesis asserts that it is necessary that legal validity should ultimately be a function of certain types of social facts; The idea here is that what ultimately explains the validity of a law is the existence of certain social facts, in particular formal promulgation by a legislator. The second example involves the idea of two people creating a child and then becoming the child`s parents and natural caregivers. This is something that natural law theory would explain as a law of nature because it is inherent in man, and any man-made law would not be necessary for people to feel they have to act as caregivers of their child. Moreover, this school of jurisprudence represents the belief that there are laws common to all societies. This applies regardless of whether they are written or can be officially issued. Inspired by Aristotle`s theory, the Stoics developed their own theory of natural law based on Aristotle`s theory, but made significant changes and made it more ethical. According to him, the world is governed by reason.
Man`s reason is also part of this world, so if he lives according to reason, he lives according to nature or lives naturally. One of man`s duties is to obey the natural law, for according to the Stoics, the natural law is obligatory for all and the positive law must correspond to the natural law. John Locke incorporated natural law into many of his theories and philosophies, particularly in Two Treatises of Government. There is considerable debate as to whether his conception of natural law resembled that of Thomas Aquinas (filtered by Richard Hooker) or the radical reinterpretation of Hobbes, although the effect of Locke`s understanding is usually formulated in the form of a revision of Hobbes on a Hobbesian contractual basis. Locke reversed Hobbes` recipe, saying that if the ruler violated natural law and failed to protect « life, liberty, and property, » people could rightly overthrow the existing state and create a new one.  According to Rousseau, it is the duty of an individual to obey the general will, for in this way he obeys his own will. The government and the laws made must conform to the general will, and if they are unable to overthrow them, Rousseau defended in short the interest of the community and not the interest of the individual, his theory of the natural law represented the equality and freedom of men. The separability thesis, at the most general level, simply denies the overlapping naturalism thesis; According to the separability thesis, there is no conceptual overlap between the concepts of law and morality. As Hart interprets it more narrowly, the separability thesis is « simply the mere assertion that it is by no means a necessary truth that laws reproduce or satisfy certain requirements of morality, when in fact they have done so many times » (Hart 1994, 185-186). The philosophy of natural law finds expression in the Roman legal system through the division of Roman law into three different divisions – ius civil, jus gentiam and ius natural. There is also natural law equal to universal law and Gaudier`s code too. Stoic theory had a great influence on jurists during the Republican period, as many jurists began to pay more attention to natural law.
Natural law helped the Romans transform their rigid life into a cosmopolitan one. Sometimes Roman courts also applied the principle of natural law to deal with cases involving foreigners, thus contributing to the development of Roman law. Therefore, Bix interprets Thomas and Schwarzstein as views similar to the neonaturalism of Johannes Finnis, which is discussed later in Section III. Yet while a plausible argument can be made for Bix`s view, the long history of interpreting Thomas Aquinas and Blackstone as conceptual naturalists, as well as their pedagogical value in the development of other legal theories, ensures that this practice is likely to continue indefinitely.