With reference to religious liberty, it is provided in Amendment I, that " Congress shall make no law respecting the establishment of religion or prohibiting the free exercise thereof," and in the constitution as originally adopted it is declared that "no religious test shall ever be required as a qualification to any office or public trust under the United States " (Art. VI, ¶ 3). The prohibition of religious tests as a qualification for holding office is now of universal recognition throughout the United States, and originated, no doubt, with the protest in England against the exercise of authority on the part of the government, the reigning family of which belonged to one religious sect, in excluding from participation in public affairs those of other sects. This form of religious liberty has now been practically recognized in England, although complete religious equality has not been established in that country.

Some state constitutions have an additional provision analogous in its nature, that no person shall be incompetent to give evidence in court in consequence of his opinion on the subject of religion; but notwithstanding such a provision, it is usually regarded as permissible to inquire into the question whether a witness has religious convictions and a belief in punishment after death, as bearing upon the question whether he is likely to appreciate the solemn obligation of an oath; for the legal oath as administered according to forms generally in use involves an appeal to a Supreme Being. However, the object of the courts in requiring the administration of an oath to witnesses is to secure so far as practicable the speaking of the truth, and the oath may be varied so as to impose upon the witness in the manner most effectual as to him the obligation to speak the truth.

Religious toleration is also the rule in all states, and involves as it is sometimes expressed the right to worship God according to the dictates of one's own conscience. But as a civil right, religious freedom is broader than this and involves freedom from compulsion with reference to any religious observances. The establishment of any religion by the state is inconsistent with religious liberty, for it must necessarily result in some discrimination against or compulsion upon persons who conscientiously adhere to some other form of religion or are not believers in any religion. The union of church and state in any form or for any purpose is inconsistent with our constitutional theory of government. It is widely recognized in the United States as beyond the proper functions of civil government to concern itself with the religious beliefs of its subjects, so far as such beliefs do not lead to actions inconsistent with the public health, public morals, or general welfare of the people. In other words, government concerns itself with acts rather than with beliefs or motives.

Complete religious liberty does not, however, necessitate an ignoring in public affairs of the fact that men in general entertain religious beliefs and that the Christian religion is the predominating form of religious belief among the people of the United States. Forms of religious observances in accordance with the accepted doctrines of Christianity are generally recognized or acquiesced in by public authorities. Thus, it is customary in the houses of Congress, and in many if not all of the legislative bodies in the states, to have the proceedings opened with public prayer offered in accordance with the general beliefs entertained by Christian denominations, although it is not usual to give any preference or exclusive privilege to the forms practised by one denomination over those of others. It is customary also for the president of the United States and the governors of the various states by public proclamation to set apart a special day in each year for thanksgiving; and special occasions for thanksgiving are sometimes indicated in the same way. Chaplains are appointed and paid by the federal government to perform religious offices in the army and navy and by state governments in the various state institutions. By law ministers of the gospel and other religious teachers are sometimes exempt from jury service and prohibited from testifying as to communications made to them in their religious capacity. These various provisions are not in the nature of the establishment of religion, or any form of religion, but rather in recognition of the fact that by general custom religion is considered not inimical to but rather promotive of the public welfare.