Linkages between Natural and International Law, with an Emphasis on Grotius Viewpoint

The fundamental question in the two Roman and Greek traditions of the philosophy of law is whether law is based on practice or idea. In the present study, we look at this question from the points of view of the following three thinkers: Thomas Hobbes who is considered to be a realist in the political science literature, Immanuel Kant who is known as an idealist, and Hugo Grotius who is regarded to be a rational and moderate philosopher. These three well-known scholars had a place in the Age of Enlightenment, which was preceded by the Scientific Revolution, and has been extolled as the foundation of modern Western political thought and ideals such as free speech, liberty and advancement.
“Natural rights” is a concept in the philosophy of law, which initially was the subject of resistance and enmity of the two groups of clerks and administrative officials.  Natural rights are given to all humans; and they are presumed to be inalienable rights, which cannot be controlled and taken away by church and/or state. They are universal and enjoyed by all human beings regardless of their dissimilarities. Accordingly, all the theological and non-theological systems of law need to be defined with no abuse of natural rights. In the dominant viewpoints in the Age of Enlightenment, it is assumed that if natural rights are unchallengeable and seemingly definite, they initially lead to a natural state of interstate relations in the international system, in which the entities are equal and not subjected to control by an overruling authority. This means that universal and unrestrained law exist for all the parties involved.
The main differences between Hobbes, Grotius and Kant concerning the link between natural rights and international law pertains to the shadow of the former over the latter. According to Hobbes, the international system is best described as the “state of nature” where life is “nasty, brutish, and short”. The rights of states are similar to natural rights of  human beings, which are unconditional or not subjected to anyone’s approval. Hobbes believes that the international society is not a civilized or lawful one. From Grotius’s standpoint, the international system is based on a long-term view of human rights. Because of the consideration of the future, some parts of the recognized rights are sacrificed in order to guarantee security and other common interests in the long-term. This is very similar to what Hobbes describes as the “civilized state”. The difference is that instead of defining a civilized system as the type which is based on the authority of one entity (e.g., a dominant and controlling power), Grotius describes it as a system characterized by dynamism. In contrast to Hobbes who calls the inter-state relations “natural”, Grotius suggests that a civilized system is the one based on substantive law. It is a system, which is not based on authority and an assured guarantee; and in fact, it is based on the long-term interest of the players (i.e., governments). Thus, the Grotius system is a legal system, particularly under the umbrella of natural rights.
Kant, as an idealist philosopher, originally presents the international system with an ultimate solution (i.e., a global government with military power and viable guarantee for its decisions). Subsequently, he makes a compromise by suggesting a more concrete and realistic plan which is closer to what Grotius had introduced. The difference is that Kant offers some regulations for the international system; and his views which are strongly influenced by natural rights are closer to the current human rights debates. In the movement from realism to idealism, the international system becomes more legal, civilized, sensitive and loyal to natural rights. Grotius offers a more moderated and systematic solution in this spectrum.
The authors concluded that the natural state of individuals lead to the civilized state, and in a similar manner, the natural state for the entities (e.g., states) in the international environment culminates in a legal state because of interests and requirements. By analyzing the writings and arguments of Grotius, Kant and Hobbes, the main differences and similarities in their points of view on the nature of the international law and relations are explained. Grotius’ solution is found to be the middle ground and realistic one, which is applicable to the contemporary international system.