Since ancient times, natural law thought has played an important role in the realms of ethics, politics, and law. Natural law theory's global validity is what makes it so compelling. It is regarded as natural law, eternal law, and divine law. The result of reason is natural law. It has gone through several stages and is described in various ways by men. The main concept of this system is morality. When determining the efficiency of human laws, morality is regarded as the superior law. Natural law was once thought to be divine or religious. It is to blame for the political and legal ideologies of today.

Natural law establishes what should be done or not done according to reason and morality. It is the factor that makes a distinction between excellent and terrible. As many jurists perceive it, it is essentially a claim to believe in a set of ideals. Natural law has been defined differently by different generations of jurists. For the Stoics, this is the divine law (Jus divindum)  God's order imposed on men. Natural law, according to Cicero, is the rule of reason since it is established by reason, which is how the universe is governed, addressed, and experienced in rational nature.

According to Aristotle and Thomasius, it is also the unwritten rule (jus non scriptum), which is written not on Brazen tablets or stone pillars, but totally with the finger of nature in men's souls. It is also known as universal or common law (jus commune, jus gentium) because it has universal legitimacy, is equal in all areas, and is binding on all people, rather than one thing in one place and another, as civil law states. According to Hooked, this is the Eternal Law that has existed since the beginning of time. Yet, according to modern jurists, natural law primarily consists of moral precepts.

Origin
The concept of natural law was understood by the ancient Greeks, although it was later developed by a large number of philosophers. Aristotle, Socrates, and Thomas Aquinas are some significant philosophers who contributed to the advancement of natural law.

It is claimed that the natural law doctrine has always existed, not even requiring the existence of governmental structures or legislative bodies. To elaborate, "natural law" encompasses the notion that people have an innate understanding of what is right and wrong.

In essence, it comes to the conclusion that natural law is not something that humans are taught, but rather, they originate it by making morally upright decisions. As a result, it is considered discoverable through the use of reason.

Definition
According to the ethical and philosophical framework known as "natural law," moral principles and the capacity for rational decision-making are essential human qualities. Good and evil can be distinguished by someone who is morally motivated. It is an inherent law of the universe that is untouched by society, culture, or custom because it is founded on human nature.

Laws should be based on ethics and morals, according to natural law, which is the moral philosophy of jurisprudence. This law also declares that the "correct" thing to do should be at the center of the law.

Humans have also discovered natural law through their ability to think and distinguish between right and wrong. It follows that it is claimed that this law is crucial in developing moral and ethical norms.

Concept
Most theories of natural law formulate some combination of survival, leading an ideal life, liberties, and happiness as the ultimate goals of humans and the fundamental ideas that constitute "morality" in their theories.

Philosophers, religious authorities, governing agencies, and theorists have engaged in several heated discussions and arguments regarding the fundamental ideas that constitute natural law, dating at least as far back as Aristotle.

The following are two statements made by Thomas Aquinas and Thomas Hobbes that are used to describe natural law:
Thomas Aquinas's Natural Law: Thomas Aquinas was a 13th-century Catholic priest and philosopher from Europe. Aquinas believed that morality and justice were a result of divine providence, or what he called the "everlasting law," which was established by the source of all morality, namely God.

According to Aquinas, the meaning and tenets of natural law are as follows:

• Humans must practise virtue and abstain from vice or sin;
• Survival and propagation are fundamental human values; and
• Natural laws established by human governments are positive laws.

European philosopher Thomas Hobbes flourished in the 17th century and is best known for his book, The Laws of Nature. Hobbes was a fervent proponent of legal positivism and characterized natural law as an agreement between people and society, while positive rules were made and upheld by a sovereign ruler.

Hobbes believed that in order for positive law to be legitimate and just, it must be in accordance with natural law, which he defined as having the following goals: liberty, happiness, survival, and prosperity.

Hobbes, on the other hand, had a negative view of human nature and thought that without a totalitarian ruler to enact and enforce laws, society would disintegrate, as he detailed in his philosophical work 'Leviathan'.

Historical development of Natural Law
Ancient thinkers like Aristotle and Plato are credited with developing the concept of natural law. Although Plato didn't have a theory on natural law, some of his theories had ideas related to it.

Aristotle, on the other hand, concentrated on the contrast between law and nature. The Stoics are responsible for the development of natural justice as a result of this.

Then Cicero contrasted positive law, which would contribute to society's safety, with natural law, which can assist in the latter's overall well-being. The theory of natural law continues to receive numerous additions, for example, in the Renaissance and Age of Enlightenment. Modern natural law theories were developed as a result, fusing social contract theory and other philosophies.

Also, it was used as justification for the creation of positive law and, as a result, of governmental authority and legal rights. The concurrence of positive and natural law will, in general, be cited, contested, and examined as philosophy theory develops.

Theories of Natural law:
Natural law is broadly classified into four categories:

1. Ancient theory
2. Medieval theory
3. Doctrine of renaissance
4. Modern theory

Natural law theories in Ancient Period
Greek period
The Greeks are thought to have been the first Ancients to discover and establish the fundamentals of natural law. A lack of political stability in Greece at the time prompted jurists to consider creating new, universal principles to combat and restrain arbitrary rulings and tyranny. Greek philosophers held that if there is anything that is universally true, it is true by nature for all mankind, regardless of time and place, according to their philosophy. Moreover, nature is a force that is independent of human influence.

Socrates
An enlightened master who trusted in human knowledge, he was reasonable in his thinking. The higher law, in his opinion, is moral. He contends that every person possesses insight, which enables them to discern what is good and harmful, and that they should act on this knowledge. In his opinion, a man can instill moral ideals in himself by his knowledge. One of the primary requirements of the time was for Natural Law to ensure the safety and stability of the nation. The same view was backed by Plato, his student. But, Aristotle is the one who develops the theory in a way that is appropriate and reasonable.

Plato
The subsequent discussion of natural law concerns greatly influenced Plato's work. He believed that all men were endowed by God with an equal sense of moral reverence and justice, enabling them to survive life's challenges. He held the view that justice is a harmony of the inner life of man, and that this harmony can be attained through the human mind and intelligence. Each person receives a specific function based on his or her abilities in his or her ideal world.

Aristotle
Natural law is credited to Aristotle as its originator. According to his logic, nature created the entire world. He asserts that man is a part of nature in two ways: first, he is one of God's created beings, and second, he has insight and reason, which enable him to exercise free will. Man can learn the timeless justice concept through reason. The rule established by reason is known as "natural justice" since man's reason is a component of nature.

Positive law should attempt to incorporate "Natural Law's" laws into itself, but it should still be upheld even if it does not contain the fundamental rule of Natural Law. Rather than breaking the law, it should be changed or amended. In his view, slaves had no choice but to accept their fate because slavery was a "natural" institution.

Ancient Rome
Roman law was significantly influenced by natural law. The restricted and inflexible Roman system was made cosmopolitan by applying natural law. Jus civile, or civil law, was one of their three categories of law, and it only applied to Roman citizens. The law that applies to visitors is known as jus gentium.

In addition, jus naturale was the law established by nature, which was unchangeable and superior to all laws made by humans and justified in every way. Roman judges applied laws common to foreign laws and to residents of other countries based on the principles of natural law.

Jus genitum is the name of the body of laws that emerged through these processes. These statutes were seen as having universal legal standards and exhibiting a strong sense of fairness.

When Roman citizenship was later expanded throughout Europe, jus civile and jus genitum merged into one. Roman lawyers all agreed that Natural law would always take precedence over Positive law whenever there was a conflict between the two.

Cicero
The highest reason, according to Cicero, is the law, which receives its legitimacy from nature. He believed that there is a divine purpose built into the universe, which is sometimes more or less comparable to the natural ordering of the divine. Due to his capacity for reason and the fact that his well being is the ultimate objective of his creation, man is the greatest possible creation. As a result, this reason dictates what should be done and what shouldn't be done. The ability to judge justice and injustice is a function of human reason.

Stoics
The Stoics adopted Aristotle's ideas as a basis for their concept of natural law making significant changes to it to make it more moral. He believes that reason underlies all of reality. As man's thinking is a component of this world as well, when he lives under reason, he is acting naturally or per nature. According to the Stoic law of nature is applies to all, and positive law must follow the natural law, one of man's obligations is to obey it.

Effect of Stoics theory:
During the Republican era, the stoic school of thought had a significant impact on the legal profession, leading many of them to start giving natural law more consideration. Romans were able to enjoy more cosmopolitan lives by applying natural law to their formerly rigid society. While natural law assisted in the creation of Roman law, the Courts of Rome occasionally applied the natural law premise to situations involving foreigners.

Roman jurists divided Rome's laws into three major groups:
Three categories of law "jus civile," "jus gentium," and "jus naturale" were recognized by the ancient Roman jurists. Roman civil law, or "jus civile," was exclusively applicable to Roman citizens, but Roman magistrates also applied foreign-law principles to foreign citizens by the "natural law" premise.

The body of law that emerged in this manner was also known as "jus gentium," and it was incorporated into Roman law. It reflected well-intentioned, universal legal concepts and followed what is known as "natural law" as a result.

As all Roman citizens, with the except of a select few, were granted citizenship, the terms "jus civile" and "jus gentium" later merged into one. But even then, there was a notion of natural law that remained unchanged while slaves were still denied the advantages of the new rule.

Ancient India
The judicial system in India is arguably the oldest in the world. Early on, they created a corpus of legislation that was exceedingly logical and thorough. Everything of law is infused with a sense of justice. But multiple foreign wars, one after another, and frequent democratic structure and government changes precluded its methodical and organic development. The research of this judicial framework was not permitted while this country was governed by a foreign power. Its many theories and guiding concepts are still largely unexplored.

The questions that cannot be resolved with great clarity include whether or not there was a concept of "Natural Law," as well as if there was, what its authority and relationship to "Positive Law" was.

Certain guidelines and rules can be mentioned in this regard, nevertheless.

From the Hindu perspective, God is responsible for the creation of law. Law is outlined in the Shruti and Smritis. The monarch is only required to carry out that law, and as he is also bound by it, he should be disobeyed if he violates it. There are numerous occasions in the Puranas where rulers were overthrown and executed for disobeying the law.

Natural law theories in the Medieval Period
The metaphysical and theological beliefs of the Catholic Church were influenced by speculative notions during the Middle Ages, and they developed their concept of Natural law.

In a world developing from the Middle Ages, there was no governmental stability at the time. The battle between both the church and the state was just getting started, and the church needed to cement its dominance. Several Catholic theologians and philosophers developed ideas that were more rational and methodical to maintain stability. The Summa Theologica, which is his most well-known work, was written by Thomas Aquinas, who was the most important author using the conventional view of natural law.

Thomas Aquinas
The relationship between causes and goals served as the foundation for Thomas Aquinas' thought. He asserts that an action and its outcome are related like things. Things naturally have the propensity to evolve in a particular manner. Despite not freezing, the fire still burns. The human mind can able to understand how the methods and ends relate to one another. It is up to him to decide on a specific goal and come up with legal strategies for how to get there.

He described the law as "an ordinance of reason for the common good made by him who has the care of the community and promulgated". He further separated law into four groups:

• Eternal Law (Lex aeterna)
• Natural Law (Lex Naturalis)
• Divine Law (Law of Scriptures)
• Human Laws (Lex Humana)

Since he believed that man is a social animal who can judge what is right by expressing his inclinations and nature, natural law was that portion of the eternal law that may be disclosed by reason, as per Aquinas, who also believed that moral law is an unchanging law.

The church is authorized to establish divine law since it is an eternal law that has been revealed through the bible. Human laws are those that the state enacts for the protection and welfare of its citizens. These regulations must, nevertheless, follow natural laws.

He coined the expression "Lex iniusta non est lex," which means an unconstitutional law is not a law, and such unfair laws should not be obeyed, to describe laws that are conflict with natural law as being unjust. The natural law was expanded upon by Hugo Grotius. He claims that natural law is so unchangeable that even God cannot alter it, proving that it is independent of all divine forces and would still be in effect in the absence of God.

He said that human nature, natural law, and positive law are the grandparents, parents, and children, respectively, of the natural law, which is dependent upon man's nature. He also addressed how people with the tendency to form intellects and a need for unity in society create a democratic agency, from which the fundamentals of natural law flow.

Merits of Aquinas's theory
Aristotle's theory and Christian faith were expertly merged by Thomas Aquinas to create a flexible and comprehensible system of natural law. Since even the sovereign has some limitations, he argued for establishing the church's supremacy over the state.

He firmly argued for preserving social stability, sanctifying social and political institutions, and connecting natural law with reason. Aquinas' theory has been expanded upon by Catholic modern jurists, who have adjusted it to fit the times and the demands of the day.

Doctrine of renaissance
All areas of knowledge underwent significant change during this period due to the birth of new theories, the development of new fields of study, and scientific advancements that upended long-held beliefs.

Second, new classes emerged as a result of innovations in business that demanded greater state protection. The idea of nationalism was born as a result. The influence of the church was overthrown when all these things came together.

There have been some recent developments in state sovereignty theories. All of these hypotheses were built based on the reason. There are some similarities between modern natural law ideas. The premise of this idea is that society is built on a social contract.

The following are some of the major Renaissance authors:
Hugo Grotius
The "social contract" formed the basis for Grotius' legal philosophy. He believes that political society is based on a "social compact," to put it briefly. The sovereign owes it to the people to protect them because it is the sole reason they were given power. The "Natural Law" binds the sovereign. Man's "reason" can find the Law of Nature. He deviated from St. Thomas Aquinas' scholarly conception of Natural Law and "reason," focusing instead on "proper reason," or "self-supporting reason" of man.

Grotius was primarily concerned with maintaining the current global peace and political order. Hugo Grotius is regarded as the father of contemporary international law, and with good reason.

He promoted the idea that all states are equal and have the right to control both their domestic as well as international relations.

Thomas Hobbes
Hobbes claimed that before the "social contract," man lived in a disordered state of continual anxiety. "Solitary, poor, nasty, brutish, and short" best describes life in the wild. Consequently, men willingly entered into contracts and gave up their freedom to a powerful institution that could secure their existence and possessions to ensure their protection and prevent misery and pain.

As a result, Hobbes believed that a ruler should have total power and that his subjects should have no recourse against him. Even if he suggests that the monarch should be governed by "Natural Law," this is only a matter of morality. So, it would be clear that Hobbes employed the notion of Natural Law to defend the sovereign's unquestionable authority.

John Locke
Locke thought that nature was in a perfect state, but that property was unstable. Men joined into the "social contract" to protect their possessions. Only a portion of man's rights, namely, the ability to uphold justice and uphold the laws of nature were ceded under the terms of this bargain. His Natural Rights, which included the freedoms of life, liberty, and property, belonged to himself alone.

Upholding and defending Natural Rights is the aim of both law and government. The laws issued by the government are legal and enforceable as long as it continues to pursue this goal; however, if it stops fulfilling this goal, the laws become invalid and the government is susceptible to overthrow. Locke fought for a legally constrained government.

As a result of people's liberties in areas of socioeconomic development, which found backing in Locke's theory, the nineteenth ideology of "laissez-faire" was born.

Jean Rousseau
According to Rousseau, the concept of the "social contract" is only an abstract idea and not a historical reality as Hobbes and Locke believed. Life was good and men were treated equally before the so-called "social contract".

People banded together to protect their justice and liberty, and to do so, they ceded those rights to the entire community, which Rousseau referred to as the "public will," rather than to a single person, or monarch. Because doing so directly observes his own will, it is everyone's responsibility to obey the "universal will".

Social Contract theory
The Renaissance era and the movements that took place in Europe and America paved the door for people to achieve spiritual liberation. Social absolutism required a legal foundation for its assertion of unrestricted power over the populace. The social contract legal theory was the one that the participants in the political dispute utilized.

Social contract theory is a fictitious application of logic. According to the common understanding of the social contract, men in ancient civilizations existed only per the laws of nature and were subject to the whims of the elements. A few scholars believe that the condition of nature was filled with suffering and repression, while others believed it to be one of joy and peace.

Hobbes, Locke, and Rousseau were the principal proponents of the social contract hypothesis.

Natural law theories in Modern Period
Nineteenth Century
Declining popularity of Natural Law theories
Natural law theories mostly represented the significant economic and political developments that had occurred in Europe throughout the nineteenth century, which saw the demise of natural law.

The philosophy of eighteenth-century thought was rationalism or cause. Remedies that were both political and practical were required to fix the issues brought on by the recent upheavals and advancements.

Individual freedom gave way to a socialistic cultural outlook, and contemporary political ideologies began to argue the absence of unalterable, universal facts. Numerous scholars disproved the social contract thesis by calling it a myth. Natural law suffered severe damage as a result of all these reasons.

Twentieth Century
The revival of Natural law theories
The "Natural Law" doctrines experienced a resurgence around the close of the nineteenth century. There were numerous causes for it: Firstly, there should be a backlash against nineteenth legal theories that inflated the significance of "positive law," and theories that overemphasized positivism did not fulfill the hopes of the public because they refused to acknowledge ethics and "reason" as components of the law. The second realization was that causal predictions or abstract reasoning were not entirely useless.

Finally, the effects of materialism on society and the altered sociopolitical climate forced legal intellectuals of the 20th century to search for a valuation philosophy that could stop the overall moral decline of the populace. The above elements combined to bring back Natural Law theory, albeit in a revised version that differs from the original. Rudolf Stammler, Prof. Rawls, Kohler, and others became the leading proponents of the newly revitalized Natural Law.

Criticism

• The doctrine of natural law is one of the most challenging because different people have understood nature differently. Would this be the case if natural law theory is correct in its claim that human reason can understand the moral law that governs human nature?
• The spread of the ideas of democracy, human rights, and equity worldwide.
• It is founded on logic rather than revelation, which enables everyone to adhere to the ideals. Because it is absolute and universal, it is always applicable.
• It sets common standards and enables a straightforward moral philosophy.
• It was used by both the French and Americans during the French Revolution in their respective wars of dependency.

Conclusion
Natural law has undergone some evolution over time, according to an in-depth assessment of its doctrines. Almost all ideologies, including absolutism and individualism, have used it as evidence. Natural law has had a significant impact on the advancement of positive legislation and has also motivated numerous conflicts.

In order to satisfy the goals of the law, which would constitute an incomplete study of the subject, Natural Law theories have been created. As a result, it is possible to assert that practically every nation's judicial structure is based on natural law ideas.

The fundamental rights guaranteed by the Indian Constitution, such as the right to life and the right to equality, are all founded on the precepts of natural law. In addition, the concept of natural justice also is premised on the precepts of natural law.

In essence, it comes to the conclusion that natural law is not something that humans are taught; rather, they originate it by choosing the appropriate course of action. As a result, it is referred to as being discoverable through the use of reason.