It guarantees that individuals have freedom of religious expression and practice and the government will not recognize any one faith as more valid than others or will not promote religion over secularism. More and more clarifications were added as and when cases of use of public property for displaying religious objects or use of public places to promote religious idea started coming in.
In Lynch V. Donnelly Case : No. 82-1256 (1983-1984) (Hirsley 1991), there was a dispute on use of religious symbols in public places. The City of Pawtucket RI erected a Christmas display as part of its celebration during Christmas festival. The display included a 'creche' that consisted of tradition figures of Infant Jesus, Mary and Joseph. The district court found it against the First Amendment and ordered its removal but in the landmark judgment by Supreme Court, they held that in spite of its religious significance the City of Pawtucket did not violate the Establishment clause and allowed the crche to remain on display. It observed that an absolute separation is not possible between Government and religion.
In another important case: Engel v. Vitale, 370 US 421 (1962), there was a dispute over the rendering of religious prayers in schools. A group of parents challenged the prayer as "contrary to the beliefs, religions, or religious practices of both themselves and their children." The state's highest court upheld the use of the prayer, on the grounds that state law did not force any student to join in the prayer over a parent's objections. But the Supreme Court found it against the spirit of Establishment clause. This again caused a lot of furor and led to many a debate in the society.
In the same vein, the issue of congressional prayers also led to lot of discussions. There has been a long-standing practice of saying prayers before the start of legislative sessions in many states. For e.g. In Maine a clergy member suggested by the lawmaker leads the prayer. Most prayers are brief and ask for God's guidance. A 1983 U.S. Supreme Court decision found that legislative prayers do not violate the principle of separation of church and state. The court described the longstanding practice as a "tolerable acknowledgement of beliefs."
In Conclusion, we can safely say that though Religion and State should be kept separate, it is not possible to have absolute separation and some connection between the two in inevitable.
Daniel L. Dreisbach. Thomas Jefferson and the Wall of Separation Between Church and State , New York University Press, 2003)
" Everson v. Board of education", 1947
Hirsley, Michael. "Religious Display Needs Firm Court."Chicago Tribune, 20 December 1991.
Kilman, J. & Costello, G. (Eds). (2000). The Constitution of the United States of America: Analysis and Interpretation.
List of United States Supreme Court Cases, Volume 370
"Lynch V. Donnelly", 1983
Thomas Jefferson: Writings: Autobiography / Notes on the State of Virginia /