Establishment Clause in the context of "First Amendment to the Constitution of the United States"

The Free Exercise Clause accompanies the Establishment Clause of the First Amendment to the United States Constitution. The Establishment Clause and the Free Exercise Clause together read:

Free exercise is the liberty of persons to reach, hold, practice and change beliefs freely according to the dictates of conscience. The Free Exercise Clause prohibits government interference with religious belief and, within limits, religious practice. To accept any creed or the practice of any form of worship cannot be compelled by laws, because, as stated by the Supreme Court in Braunfeld v. Brown, the freedom to hold religious beliefs and opinions is absolute. Federal or state legislation cannot therefore make it a crime to hold any religious belief or opinion due to the Free Exercise Clause. Legislation by the United States or any constituent state of the United States which forces anyone to embrace any religious belief or to say or believe anything in conflict with his religious tenets is also barred by the Free Exercise Clause.

Intelligent design (ID) is a pseudoscientific argument for the existence of God, presented by its proponents as "an evidence-based scientific theory about life's origins". Proponents claim that "certain features of the universe and of living things are best explained by an intelligent cause, not an undirected process such as natural selection." ID is a form of creationism that lacks empirical support and offers no testable or tenable hypotheses, and is therefore not science. The leading proponents of ID are associated with the Discovery Institute, a Christian, politically conservative think tank based in the United States.

Although the phrase intelligent design had featured previously in theological discussions of the argument from design, its first publication in its present use as an alternative term for creationism was in Of Pandas and People, a 1989 creationist textbook intended for high school biology classes. The term was substituted into drafts of the book, directly replacing references to creation science and creationism, after the 1987 Supreme Court's Edwards v. Aguillard decision barred the teaching of creation science in public schools on constitutional grounds. From the mid-1990s, the intelligent design movement (IDM), supported by the Discovery Institute, advocated inclusion of intelligent design in public school biology curricula. This led to the 2005 Kitzmiller v. Dover Area School District trial, which found that intelligent design was not science, that it "cannot uncouple itself from its creationist, and thus religious, antecedents", and that the public school district's promotion of it therefore violated the Establishment Clause of the First Amendment to the United States Constitution.

"Separation of church and state" is a metaphor paraphrased from Thomas Jefferson and used by others in discussions of the Establishment Clause and Free Exercise Clause of the First Amendment to the United States Constitution, which reads: "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof".

The principle is paraphrased from Jefferson's "separation between Church & State". It has been used to express the understanding of the intent and function of this amendment, which allows freedom of religion. It is generally traced to a January 1, 1802, letter by Jefferson, addressed to the Danbury Baptist Association in Connecticut, and published in a Massachusetts newspaper.

Kitzmiller v. Dover Area School District, 400 F. Supp. 2d 707 (M.D. Pa. 2005) was the first case brought in the United States federal courts testing a public school policy requiring the teaching of intelligent design (ID). The court found intelligent design to be not science. In October 2004, the Dover Area School District of York County, Pennsylvania, changed its biology teaching curriculum to require that intelligent design be presented as an alternative to evolution theory, and that Of Pandas and People, a textbook advocating intelligent design, was to be used as a reference book. The prominence of this textbook during the trial was such that the case is sometimes referred to as the Dover Panda Trial, a name which recalls the popular name of the Scopes Monkey Trial in Tennessee, 80 years earlier. The plaintiffs successfully argued that intelligent design is a form of creationism, and that the school board policy violated the Establishment Clause of the First Amendment to the United States Constitution. The judge's decision sparked considerable response from both supporters and critics.

Eleven parents of students in Dover, York County, Pennsylvania, near the city of York, sued the Dover Area School District over the school board requirement that a statement presenting intelligent design as "an explanation of the origin of life that differs from Darwin's view" was to be read aloud in ninth-grade science classes when evolution was taught. The plaintiffs were represented by the American Civil Liberties Union (ACLU), Americans United for Separation of Church and State (AU) and Pepper Hamilton LLP. The National Center for Science Education (NCSE) acted as consultants for the plaintiffs. The defendants were represented by the Thomas More Law Center (TMLC). The Foundation for Thought and Ethics, publisher of Of Pandas and People, tried to join the lawsuit late as a defendant but was denied for multiple reasons.