What purpose is served by the preamble of the Indian Constitution?

The purpose of the Preamble is to clarify who has made the Constitution, what is its source, what is the ultimate sanction behind it; what is the nature of the polity which is sought to be established by the Constitution and what are its goals and objectives. The words in the Preamble, ‘We the people of India….in our Constituent Assembly…do hereby adopt, enact and give to ourselves this Constitution”, propound theory that the ‘sovereignty’ lies in the people, that the Constitution, emanates from them; that the ultimate source for the validity of, and the sanction behind the Constitution is the will of the people; that the Constitution has not been imposed on them by any external authority, but is the handiwork of the Indians themselves.