In the Lettres philosophiques, Voltaire had suggested a more radical position with respect to human determinism, especially in his letter on Locke, which emphasized the materialist reading of the Lockean soul that was then a popular figure in radical philosophical discourse. Some readers singled out this part of the book as the major source of its controversy, and in a similar vein the very materialist account of “Âme,” or the soul, which appeared in volume 1 of Diderot and d’Alembert’s Encyclopédie, was also a flashpoint of controversy. Voltaire also defined his own understanding of the soul in similar terms in his own Dictionnaire philosophique. What these examples point to is Voltaire’s willingness, even eagerness, to publicly defend controversial views even when his own, more private and more considered writings often complicated the understanding that his more public and polemical writings insisted upon. In these cases, one often sees Voltaire defending less a carefully reasoned position on a complex philosophical problem than adopting a political position designed to assert his conviction that liberty of speech, no matter what the topic, is sacred and cannot be violated.