The Preamble to the Constitution of India presents the
principles of the Constitution and indicates the sources of its authority. It
was adopted on 26 November 1949 by the Constituent Assembly and came into
effect on 26 January 1950, celebrated as the Republic Day of India. It was
amended during the Indian emergency by Indira Gandhi where the words
"socialist", "secular" and "integrity" were
added.
The preamble is based on the Objectives Resolution, which
was moved in the Constituent Assembly by Jawaharlal Nehru on 13 December 1946
accepted on 22 January 1947 and adopted by the Constituent Assembly on 26
November 1949, coming into force on 26 January 1950.
B. R. Ambedkar said
about the preamble:
It was, indeed, a way of life, which recognizes liberty, equality, and fraternity as the principles of life and which cannot be divorced from each other: Liberty cannot be divorced from equality; equality cannot be divorced from liberty. Nor can liberty and equality be divorced from fraternity. Without equality, liberty would produce the supremacy of the few over the many. Equality without liberty would kill individual initiative. Without fraternity, liberty and equality could not become a natural course of things.
Ref: Wikipedia.