"By the mid-century many of the younger educated ministers prided themselves on their broad-minded rational theology. The Calvinist self-righteousness of the persecuted sect was left behind, and they gravitated through Arian and Socinian "heresy" towards Unitarianism. From Unitarianism it was only a further step to Deism, although few took this step until the 1790s; and even fewer in the second half of the 18th century wished or dared to make a public avowal of scepticism—in 1763 the seventy-year-old schoolmaster, Peter Annet, was imprisoned and stocked for translating Voltaire and for publishing "free-thinking" tracts in popular form, while shortly afterwards the sceptical Robin Hood debating society was closed down. It was from Socinian or Unitarian positions that liberal principles were argued: the famous figures are Dr. Price, whose Observations on Civil Liberty (1776) at the time of the American War achieved the remarkable sale of 60,000 within a few months, and who lived to enrage Burke by his sermon in welcome to the French Revolution; Dr. Priestley himself; and a score of lesser figures, several of whom— Thomas Cooper of Bolton and William Frend of Cambridge— took an active part in the reform agitation of the 1790s."