Journalist Susan Jacoby is the director of the Center for Inquiry Metro New York, a rationalist research and advocacy organization. She is the author of seven books, including "Wild Justice: The Evolution of Revenge," which was nominated for the Pulitzer Prize. Jacoby's latest book is "Freethinkers: A History of American Secularism." Jacoby spoke with Beliefnet about America's secular beginnings, freethought heroes, and the battles ahead between secularists and the religious right.

What does "freethinker" mean?
Freethinker and freethought are terms that date from the end of the 17th century. Freethinker basically meant someone who did not believe in the received word of the bible or the authority of religion. Freethinkers have often been described as people who didn't believe in God, but it's more accurate to see freethought as a kind of a broad continuum, ranging from those who really didn't believe in God at all to deists who believed in a God who set the universe in motion but afterwards didn't take an active role in the affairs of men.

By the end of the 19th century, freethinkers even included liberal Protestant denominations and Unitarians. Even though they believed in God and in some form of Christianity, they did not believe in any hierarchy of religion. So there was a spectrum of people in the freethought community, but all were opposed to the religious orthodoxies of their day.

Who would the term freethinker encompass today?
I would say my definition of freethinker from the past is just as good a definition of freethinker today. I prefer it to agnostic or atheist or deist or anything else you might come up with. It also encompasses the belief that if God did create man, he created rationality as the supreme instrument for understanding the natural world. Freethinker is kind of an archaic word, but it's very descriptive.

More descriptive than Bright, for example?
I think Bright is an idiotic term. It did not exactly get a rousing response, even from the non-believing community.

You categorize liberal Protestants as a type of freethinker. Do you think a liberal Protestant today would accept being called a freethinker by you?
That's an interesting question. It's a kind of archaic word, so I don't know. I know Unitarians would be happy to be called freethinkers. It's hard to tell when you're using a word which once had a very strong meaning and now is just sort of being revived.

Let's turn to the history of secularism. How does this history fit into American religious history?
The secularist strain in American culture has been very strong since the beginning, but the nation's secular heritage is virtually unknown to people. A secular government was developed to protect the rights of religious minorities. Most Americans don't know that God is not mentioned in the Constitution. It was a coalition of religious Evangelicals and freethinkers or deists who joined together to get this ratified. And why did the Evangelicals want this then? Because they were a minority and they deeply feared government interference with religion. This Constitution basically placed the Episcopal Church, the established religion in the South before the Revolution, on a level playing field with all of the Evangelical Protestant denominations that were sprouting up. The effect of this was to enable them to proselytize for their own religion in ways that if there had been a union of established church and state they never would have been able to do. Ironically, it's the separation of church and state that has probably enabled religion to flourish throughout the 20th century in this country in ways that it doesn't in other developed nations.

The history of secularism is also the history of a certain kind of religion. One of the interesting things that happened in this country is, between roughly 1780 and 1825 in New England, more than half of all of the once orthodox Calvinist churches transformed into the much more liberal, Unitarian churches, a development the orthodox of the day hated as much as the religious right hates secularists today. In fact, they referred to Unitarians as infidels and atheists. But those people led to a transformation of American religion. They were influenced by freethought and freethinkers were influenced by them. And later on when evolution came along, this part of American Protestantism accommodated itself to evolutionism, as it had accommodated itself to Enlightenment thought in the 18th century.

What was the period you call the "Golden Age of Freethought?"
The Golden Age of Freethought lasted from about 1870 to the first World War. It was an era in America when the influence of science was expanding and a lot of people were looking for answers to the meaning of life, which religious orthodoxy didn't satisfy. The Golden Age of Freethought was very closely connected to the dissemination of Darwin's theory of evolution.