Indian constitution historical underpinnings, The preamble of the Constitution of India is the heart and soul of the Constitution. The preamble can be referred to as the preface which highlights
the entire Constitution. It was adopted on 26 November 1949 by the Constituent Assembly and came into effect on 26 January 1950. And the day is celebrated as Republic day in India. As originally enacted the preamble described the state as a "sovereign democratic republic", to which the terms "Secular" and "Socialist" were later added by the 42nd Amendment.
WE, THE PEOPLE OF INDIA, having solemnly resolved to constitute India into a SOVEREIGN SOCIALIST SECULAR DEMOCRATIC REPUBLIC and to secure to all its citizens
 JUSTICE, social, economic and political;
 LIBERTY of thought, expression, belief, faith and worship;
 EQUALITY of status and of opportunity; and to promote among them all
 FRATERNITY assuring the dignity of the individual and the unity and integrity of the Nation;
Sovereignty means the independent authority of a State. It means that it has the power to legislate on any subject; and that it is not subject to the control of any other State or external power. the word ‘sovereign’ is taken from article 5 of the constitution of Ireland. Sovereignty has two aspects- external and internal.
External sovereignty means the independence of a country of the will of other country in international law.
Internal sovereignty means the relationship between the states and the individuals within its territory. Internal sovereignty relates to internal and domestic affairs, and is divided into four organs, namely, the executive, the legislature, the judiciary and the administrative.
 The term socialist means to democratic socialism, i.e. achievement of socialist goals through democratic, evolutionary and non-violent means. through distributive justice, not concentrated in the hands of few, and that the government should regulate the ownership of land and industry to reduce socio-economic inequalities.
By the 42nd Amendment in 1976, the term "Secular" was also incorporated in the Preamble. the term "Secular" means There is no difference of religion i.e. all religion are equally respected and there is no state religion. All the citizens of India are allowed to profess, practice and propagate any religion.
The term Democratic means that The people of India elect their governments by a system of universal adult franchise, known as "one man one vote". Every citizen of India 18 years of age and above and not debarred by law is entitled to vote. The word 'democratic' not only refers to political but also to social & economic democracy.
The Word Republic means the head of state is elected and not a hereditary monarch. the republic is an entity in which the head of state is elected, directly or indirectly, for a fixed tenure. Thus, India has a President who is elected and has a fixed term of office for the five years.
India seeks social, economic and political justice to ensure equality to its citizens.
Social Justice means the absence of socially privileged classes in the society and no discrimination against any citizen on the basis of caste, creed, color, religion, gender or place of birth. India eliminating all forms of exploitations from the society.
Economic Justice means no discrimination between man and woman on the basis of income, wealth and economic status. equitable distribution of wealth, economic equality, the end of monopolistic control over means of production and distribution, decentralisation of economic resources, and the securing of adequate opportunities to all for earning their living.
Political Justice means equal, free and fair opportunities for the all indian citizen to participate in the political process. It grant of equal political rights to all the people without discrimination. The Constitution of India provides for a liberal democracy in which all the people have the right and freedom to participate.
Liberty means The idea of Liberty refers to the freedom on the activities of Indian citizens in term of what they think, their manner of expressions and the way they wish to follow up their thoughts in action. However, liberty does not mean freedom to do anything, and it must be exercised within the constitutional limits.
Equality envisages that no section of the society enjoys special privileges and individuals are provided with adequate opportunities without any discrimination: all are equal before the law.
Fraternity refers to a feeling of brotherhood and a sense of belonging with the country among its people. It leaves no room for regionalism, communalism, casteism etc., which hinders the Unity of the State.
The Preamble declares that fraternity has to assure two things—the dignity of the individual and the unity and integrity of the nation. The word 'integrity' has been added to the Preamble by the 42nd Constitutional Amendment (1976).
It has been clarified by the Supreme Court of India that, being a part of the Constitution, the Preamble can be subjected to Constitutional Amendments exercised under article 368, however, the basic structure cannot be altered.
The preamble has been amended only once so far. On 18 December 1976, during the Emergency in India, the Indira Gandhi government pushed through several changes in the Forty-second Amendment of the constitution. A committee under the chairmanship of Sardar Swaran Singh recommended that this amendment the words "socialist" and "secular" were added between the words "Sovereign" and "democratic" and the words "unity of the Nation" were changed to "unity and integrity of the Nation".