Summations Only

The Supreme Court has said that a religion, for purposes of the First Amendment, is distinct from a "way of life," even if that way of life is inspired by philosophical beliefs or other secular concerns...A religion need not be based on a belief in the existence of a supreme being (or beings, for polytheistic faiths)...
...
Without venturing too far into the realm of the philosophical, we have suggested in the past that when a person sincerely holds beliefs dealing with issues of "ultimate concern" that for her occupy a "place parallel to that filled by...God in traditionally religious persons," those beliefs represent her religion...We have already indicated that atheism may be considered, in this specialized sense, a religion. See Reed v. Great Lakes Cos., 330 F.3d 931, 934 (7th Cir.2003) ("If we think of religion as taking a position on divinity, then atheism is indeed a form of religion.").
...
The Supreme Court has recognized atheism as equivalent to a "religion" for purposes of the First Amendment on numerous occasions...The Establishment Clause itself says only that "Congress shall make no law respecting an establishment of religion," but the Court understands the reference to religion to include what it often calls "nonreligion." In McCreary County, it described the touchstone of Establishment Clause analysis as "the principle that the First Amendment mandates government neutrality between religion and religion, and between religion and nonreligion."
...
At one time it was thought that this right [referring to the right to choose one's own creed] merely proscribed the preference of one Christian sect over another, but would not require equal respect for the conscience of the infidel, the atheist, or the adherent of a non-Christian faith such as Islam or Judaism. But when the underlying principle has been examined in the crucible of litigation, the Court has unambiguously concluded that the individual freedom of conscience protected by the First Amendment embraces the right to select any religious faith or none at all.
...
Atheism is, among other things, a school of thought that takes a position on religion, the existence and importance of a supreme being, and a code of ethics. As such, we are satisfied that it qualifies as Kaufman's religion for purposes of the First Amendment claims he is attempting to raise.