Phillips was the first case in the United States to recognize the Free Exercise Clause and its principles.
Despite that fact, a state court, the New York Court of Sessions quoted from and relied upon the Free Exercise Clause extensively in the 1813 Phillips case, finding that it was consistent with New York common law (common law is the accumulated cases and legal principles developed over time).
Phillips was particularly important because it was the first case recognizing the religious testimonial privilege in the United States. The court addressed whether a Catholic priest could be compelled to testify regarding the contents of a confession. In ringing language, the court held:
“In this country there is no alliance between church and state; no established religion; no tolerated religion—for toleration results from establishment—but religious freedom guaranteed by the constitution, and consecrated by the social compact. It is essential to the free exercise of a religion, that its ordinances should be administered—that its ceremonies as well as its essentials should be protected. The sacraments of a religion are its most important elements. We have but two in the Protestant Church—Baptism and the Lord’s Supper—and they are considered the seals of the covenant of grace. Suppose that a decision of this court, or a law of the state should prevent the administration of one or both of these sacraments, would not the constitution be violated, and the freedom of religion be infringed? Every man who hears me will answer in the affirmative. Will not the same result follow, if we deprive the Roman catholic of one of his ordinances? Secrecy is of the essence of penance. The sinner will not confess, nor will the priest receive his confession, if the veil of secrecy is removed: To decide that the minister shall promulgate what he receives in confession, is to declare that there shall be no penance; and this important branch of the Roman catholic religion would be thus annihilated.”