1. 18th-century origin
The term freethinker first appeared around 1700 in the nascent civil philosophy of religion (Religion, philosophy of) in England. In 1697 the Irish scholar William Molyneux wrote in a letter to John Locke that the pamphleteer John Toland, famous for his book Christianity Not Mysterious (1695), was a “candid freethinker” [2. 150]. Anthony Collins, an acquaintance of Locke and a friend of Toland, …