DEISM. The term deism was originally equivalent to theism, differing only in etymology: theism based on the Greek word for god (theos), and deism on the Latin (deus). In the seventeenth and eighteenth centuries, however, deism came to signify one or another form of rationalistic theological unorthodoxy. Often used pejoratively, it was also sometimes worn as a badge of honor. The first known use of the term occurs in the Instruction chrétienne (1564) of the Calvinist theologian Pierre Viret: "I have heard he is of that band who call themselves 'Deists,' a wholly new word which they would oppose to 'Atheist.'"

In its principal meaning, deism signifies the belief in a single God and in a religious practice founded solely on natural reason rather than on supernatural revelation. Thus Viret characterizes deists as "those who profess belief in God as creator of heaven and earth, but...