The constitutional requirement for a separation of church and state. Its amazing to see how many times a day this phrase is invoked in the discussion of religious rights and the interaction between religion (and religious people) and the government. But it is also interesting to see that the understanding of what that phrase means has turned exactly 180 degrees away from the way that it was understood and written by the writers of the Constitution and the Bill of Rights.
To begin with, the actual language of the First Amendment of the Bill of Rights doesnt even use the phrase separation of church and state. What it does say is this: Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the government for a redress of grievances. Just looking at the part about religion, this clearly says that the restrictions in this separation are to be on the government. The church and its members are supposed to be able to do what they are called by God to do without the government passing any law that would either establish a state-sponsored religion (like what happened in England in the 1500s, leading to lots of bloodshed when a new monarch was of a different religion than the previous one, requiring people to either change their religion or suffer the consequences) or passing any law that would prohibit the free exercise of religion, limiting how churches and religious people followed the dictates of their faith.
This was all well understood for decades, and the church and its people freely practiced every part of their faith, including not only holding worship services and Bible studies, but founding colleges, hospitals, rehabilitations centers, orphanages, adoption agencies, social service networks, homeless shelters and many more things that improved the lives of countless people. They also were able to freely share their faith in the arena of ideas without hindrance. If someone didnt want to listen, fine. But there were no government-placed limitations on who you could share your story with because the people understood that we are protected by our Bill of Rights from government interference in the exercise of our religion.
But the direction has changed, and changed markedly, in the last few decades; slowly at first, but seeming to gain speed all the time. Now it is believed that the restrictions in the separation must be placed on churches and religious people; that limitations must be placed on them to keep them from having an undue influence on the state, or even on other people. We can see this reflected in the excising of prayer from schools; in the removing of displays of the Ten Commandments and nativity scenes and even memorials with crosses on them from public lands; and even in stopping of prayers before school sporting events and, increasingly, before public meetings.
In 1798, John Adams wrote a letter to the officers of the first brigade of the 3rd division of the Massachusetts militia. In it he wrote: Our Constitution was made only for a moral and religious people. It is wholly inadequate to the government of any other. And he, along with the framers of the Constitution itself, understood that the best way to ensure that America continued to be a nation where at least the majority of people were moral and religious, was to ensure that our government allowed not just freedom of worship, but genuine freedom of religion.