Atheism, as defined by the entry in Diderot and d'Alembert's Encyclopédie, is "the opinion of those who deny the existence of a God in the world. The simple ignorance of God doesn't constitute atheism. To be charged with the odious title of atheism one must have the notion of God and reject it."[1] In the period of the Enlightenment, avowed and open atheism was made possible by the advance of religious toleration, but was also far from encouraged.
Accusations of atheism were common, but most of the people suspected by their peers of atheism were not actually atheists. D'Holbach and Denis Diderot seem to be two of the very small number of publicly identified atheists in Europe during this period. Thomas Hobbes was widely viewed as an atheist for his materialist interpretation of scripture—Henry Hammond, a former friend, described him in a letter as a "Christian Atheist".[2] David Hume was accused of atheism for his writings on the "natural history of religion";[3] Pierre Bayle was accused of atheism for defending the possibility of an ethical atheist society in his Critical Dictionary, and Baruch Spinoza was frequently regarded as an atheist for his "pantheism". However, all three of these figures defended themselves against such accusations.