• First Amendment guarantees freedom of religion
• But the precise meaning of "religious freedom" is hard to define and has changed over time

The First Amendment is immensely important to Americans; it is also woefully misunderstood. It is so deeply ingrained in our national mythology that we toss around terms like "freedom of religion" and "separation of church and state" without really thinking about what these ideas meant to early Americans—and what they mean to us now.

For example, every Thanksgiving, we celebrate the migration of religious outcasts who came to America in search of "religious freedom," but we leave out the minor detail that they meant religious freedom only for themselves. They drove all those that disagreed with them from their midst—hanging them if they refused to leave—and resisted the pleas of the English government to be a little more tolerant. We celebrate the Founding Fathers, who had the insight to create a government that insisted on the separation of church and state, but we ignore the pesky historical fact that the term "separation of church and state" does not actually appear anywhere in the First Amendment, was first used more than a decade after the ratification of the Bill of Rights, and held little of the same meaning then that we attach to it today.

So what's the real story? What do we need to know?