Furthermore, Thomas Aquinas divided his concept of natural law into two types as follows:

  1. Principia prima, which are principles that humans possess from birth and cannot be alienated from them. Therefore, principia prima cannot change according to place and time.
  2. Principia secundaria, which are principles that originate from principia prima, on the contrary, are not absolute and can change at any time and place. Often this principle is said to be a human interpretation using his reason towards principia prima. This interpretation varies, can be good or bad. An interpretation can be generally binding if positive law gives these principles binding power, for example in the form of laws.

The Doctrine of Natural Law in the Renaissance Era

During the Renaissance, the doctrine of natural law was no longer based on the concept of divinity (scholasticism), but on human reason. The founder of rational natural law was Hugo de Groot or Grotius. He wrote two famous books, namely De Jure Belli ac Pacis (on the law of peace and war) and Mare Liberium (on the law of free seas). Grotius is regarded as the founder of international law by calling it the law of nations (ius gentium). According to Grotius, this ius gentium is a natural law practiced by all nations.

According to Grotius, the doctrine of natural law originates from human reason, which is an expression of human thought whether a human behavior is considered good or bad, whether a human action can be accepted or rejected on the basis of natural morality. Because the assessment of human behavior towards one another must be based on that natural morality.

The natural law that humans find thanks to their rational activity is regarded by Grotius as a law that applies in reality just like positive law. In this case, Grotius follows the Scholastic tradition. However, he deviates from the Scholastic view by ensuring that natural law remains in force, even if God does not exist. The reason is that natural law is part of human reason as part of its essence. On the other hand, Grotius still admits that God is the creator of the universe. Therefore, indirectly God remains the foundation of natural law.

Thus Grotius also acknowledges that besides natural law that originates from human reason, there is natural law that originates from God's reason, for example, which is found in the Holy Book. Regarding this, Apeldoorn sees that Grotius is not consistent with his opinion. In "De Jure Belli ac Pacis", Grotius says that God is the creator of the universe. So the doctrine of natural law is also indirectly a creation of God.

Grotius puts forward the first rational principle in the field of law, namely that everyone has a tendency to live together with others peacefully. This tendency exists in humans regardless of their will. Therefore, this tendency can become the objective basis of all laws.

In connection with this principle, Grotius puts forward four principles that are the pillars of the entire system of natural law, namely: a) the principle of mine and yours. Other people's property must be protected. If borrowed goods bring profit, that profit must be rewarded; b) the principle of fidelity to promises; c) the principle of compensation, namely if the loss is caused by the fault of others; and d) the principle of the need for punishment for violations of natural law and other laws. These four principles are found a priori as the principle of all laws. However, that principle can also be found a posteriori, namely as a reality in all civilized nations.

Furthermore, Grotius divides the doctrine of natural law in a narrow sense and in a broad sense. In a narrow sense is the real law because it creates a right to demand that what belongs to it be given (facultas). The justice that applies in this area is the justice that pays it off (author: commutative justice). Meanwhile, natural law in a broad sense is a law that does not create a juridical right, but only a right in the form of appropriateness (aptitudo). The justice that applies in this area is the justice that gives (author: distributive justice).

Regarding the relationship between the doctrine of natural law and positive law, Grotius argues that positive law is the law that applies in a country because it is approved and ratified by the authorities. This law (positive) must not contradict natural law, namely it must not order something that is prohibited by natural law. But natural law as a limit of positive law can be passed if required by the public interest of the state.

Contrary to Grotius, Thomas Hobbes does not accept the existence of a tendency to live together in humans. According to Hobbes, since ancient times humans have been entirely controlled by natural desires to fight for their own interests. Because in the original situation there were no norms of living together, primitive people had rights over everything. Then arose what Hobbes called bellum omnium contra omnes, man became a wolf to other men (homo homini lupus).

Over time, people began to realize the advantage of securing their lives by creating a rule of living together for all people who belong to the same group. To achieve such a rule, everyone must surrender their original rights over everything and must obey some natural tendencies which Hobbes calls natural laws (leges naturales).

These natural laws are not laws in the true sense, but are only instructions that must be followed if the goal is to be achieved, such as the instructions seek peace, surrender your original rights, treat others as you want others to treat you, and keep your promises.

The importance of the principle that promises must be kept is most striking in an agreement that Hobbes calls the original contract, namely the agreement of people in a group to form a life together and orderly. This original social agreement is the origin of the state.

The Doctrine of Natural Law in the Age of Enlightenment

John Locke, like Hobbes, also explains the emergence of the state and law by describing the situation in primitive times. However, Locke was an opponent of Hobbes' theory of absolutism, by putting forward theory about inalienable individual rights.

In primitive times people lived according to the teachings of natural law. Natural laws cover various fields, namely the fields of life, health, freedom, property. In the field of life people have the right to live, in other fields they have the right to health, the right to freedom, the right to property and the right to be an heir. Violations of these rights can be punished by each individual, because at that time each person had the executive power of the law of nature.

At one time, primitive people moved from their original state to a civil state. With the transition of humans to a civil state, primitive natural law did not disappear. The law still applies, including in relations between countries. The proof is that all contracts are only valid based on a principle of natural law: promises must be kept (keeping of faith).

However, in order for the state to function as a guardian of the law, people need to surrender some of their primitive rights to the state, namely the exercise of the right to punish privately. Since the establishment of the state, it is not the people who are in charge of ensuring that personal rights are maintained, but the state and the rule of law. So the aim of the state is none other than to guarantee the personal rights of the people. The state does not have the power to revoke the natural rights of individuals.

John Locke mentions that there are three powers of the state, namely legislative, executive and federative power. The highest power is legislative power. Because that power is the highest, in forming laws the government only has to submit to natural law. Legislative power is not only found in the state. A group of people can make laws for their co-existence.

But the law only becomes valid as law because of the legislative power of the state, which is able to determine sanctions if the law is violated. However, on the other hand, the legislative power of the state government is limited, because the people have power that exceeds the legislative power.

The people have the right to regain their original freedom if the government abuses its power by acting against the aims of the state. That power is bound by natural law, which remains with the people. Thus John Locke's theory of natural law contains a revolutionary tendency: when certain conditions are not met by government, revolution is permitted.

In his book De l ‘Esprit de Lois which was later translated into English as the spirit of laws, Montesquieu stated that before all these laws existed, there was already natural law. This natural law applies fully in the existence of our own beings. To gain perfect knowledge of this law, we must imagine humans before the formation of society: the laws that take place in that state are natural laws.

The most important, though not the first, of the laws of nature is the law that is imprinted in our minds that has been made by the Creator so that we are inclined to it. Humans in a natural state have the ability to know before they gain knowledge acquired from learning. Of course his first ideas were by no means speculative ideas; he thinks to maintain his survival before he investigates his origins.

Montesquieu put forward generations of natural law teachings, which started from the natural state of humans. In a natural state humans feel helpless and excessive feelings of weakness, fear and anxiety, so that in that condition they are unlikely to attack each other; thus peace is clearly the first law of nature.

Besides this feeling of weakness, humans soon find that they have needs. From here another natural law encourages him to seek food. Besides fear making humans avoid each other, this fear also encourages humans to live in groups. In group life, attraction arises between humans of different sexes, and this natural tendency that they have towards each other is the third law of nature. Meanwhile, the fourth law of nature arises from the desire to live in society.

In his book De l’Esprit des Lois (1748) Montesquieu often shows himself as a defender of natural law. Nevertheless, he places more emphasis on the historical evolution of the various national legal orders; each nation has its own laws, which are formed from the circumstances of its past, its customs and morals, as well as by its natural environment (geographical environment, climate and so on). In this matter he deviates from natural law, by stating that the laws of all nations consist of a number of rules inspired by Reason and therefore apply universally and unchangingly which he wants to describe according to the “nature of everything” in this world.

However, Montesquieu still sees a close relationship between natural law and the concrete situation of a nation. Natural law is a law that applies to humans as humans. But how natural law is concretized in the form of state and law depends on the historical, psychic and cultural situation of a nation. So the best law is the law that is most suitable for a particular nation.

In contrast to Hobbes, Locke and Montesquieu, Jean Jacques Rousseau does not speak at all about a natural law in primitive humans. Natural law is only found in people who have entered civil society. Through the social contract, humans receive ratification of their rights as humans, both morally and legally. The social contract that gives rise to civil society originates from the will of all people who all want to realize their individual ideals.

But after the emergence of a new society, individual ideals are replaced by general ideals, which originate from a new will, namely the general will (volonte generale) which then gives rise to a common goal, namely the common interest. So if in a particular society laws are formed that do not reflect the public interest, because their validity is not the same for everyone, then the law must be considered unfair.

Immanuel Kant has a different view regarding natural law. According to him, the teaching of natural law is nothing more than the law of cause and effect, which determines nature deterministically. The background to Kant's view is the separation between the realm of 'being' and the realm of 'must', the realm of theoretical reason and the realm of practical reason. The principles of the rule of law belong to the realm of practical reason, and therefore are autonomously binding.

But the rule of law itself belongs to the realm of theoretical reason, because it is experienced as a natural phenomenon. In this theoretical field there is no obligation. Here only the laws of nature apply. If law belongs to nature, and is therefore outside the realm of morality, then it can also be understood that violence and threats may be used to maintain the rule of law.

By enforcing the rule of law in this way, moral rules are also indirectly supported. According to Kant's philosophy, laws must be formed based on general principles of law, as captured by practical reason. State regulations are the concretization of these general principles. Thus, he asserts that law only becomes law because it originates from those who have the right to form law, namely the government.

Natural Law Doctrine according to the Neo-Kantian View

Some Kantian adherents known as Neo-Kantians, such as Hans Kelsen and Rudolf Stammler, gave different opinions regarding natural law. In explaining legal rules and natural law, Hans Kelsen stated that legal rules are the logical form of the law of nature (the rule of law is the logical form of the law of nature). Like legal rules, natural law also connects two facts to each other like conditions and consequences. What is meant by condition here is "cause", consequence is "effect".

The basic form of the doctrine of natural law is the law of causality (the fundamental form of the law of nature is the law of causality). The difference between legal rules and natural law seems to be that legal rules refer to humans and their actions, while natural law refers to objects and their reactions. However, human actions can also be a study of natural law as long as human actions are also included in natural phenomena. The principle used by natural science (law) in describing its objects is causality, while the principle used by legal science in describing its objects is norms.

In contrast to Kelsen, Stammler arrived at a concept of natural law that is not eternal. This is because the basis of his natural law is human need. Because these human needs change over time and place, the result is that the natural law produced also changes over time and place. Stammler argues that the fairness of a law lies in whether or not the law can meet human needs.

Natural Law Doctrine according to Mochtar Kusumaatmadja

Mochtar Kusumaatmadja argues that law is related to human life in society, not law in the sense of exact science and nature whose object is inanimate objects. In positive law, the object being regulated is also the subject (actor). This has important consequences for scientific methods and explanations of cause and effect (causality). Positive law, which is the object of positive legal science, is not as certain as the law of natural science. As a science that studies positive law as a set of rules that regulate humans and society, it is not regulated by the scientific method of exact science and nature, but by the scientific method of the humanities.

Positive law that regulates the behavior (behavior) of humans who are not inanimate objects but living beings who have thoughts and the ability to distinguish between good and bad (ethics), has consequences not only for scientific methods but also for causality. From Mochtar Kusumaatmadja's explanation, it is clear that he sharply distinguishes between positive law and natural law and that what is most important according to him for humans is positive law.

Conclusion

Natural law is a law that applies universally and eternally. Some of this natural law comes from God and some comes from human reason. This is what distinguishes natural law from positive law where the existence of positive law depends on the will of human will. In other words, there is an order and there is a desire to follow that order, and there are sanctions from the community if the law is not obeyed.

When society lives in a state, the state institution becomes the highest authority in the formation and enforcement of legal rules through sanctions that have coercive power. Thus, positive law can be formulated as law that applies in a certain place and time where its formation and enforcement is very dependent on the will of the ruler or state.