Starting with a critical discussion of recent research on the meaning and use of the term ‘system’ in eighteenth-century France, the present paper demonstrates that it is misleading to speak of <em>the </em>‘system’ <em>tout court</em>, as the concept was employed in a variety of contexts and understood in completely different ways. With reference to key texts by Newton, Voltaire and Condillac, the relevant lemmata in the <em>Encyclopédie </em>authored by D’Alembert, Diderot and others, as well as the so-called ‘materialists’ of the second half of the century, it will be shown that a clear distinction was drawn between what Condillac referred to as “systèmes abstraits” and “systèmes vrais”: Whereas the former, being based on mere supposition and epitomized in the works of Descartes and Spinoza, were rejected, the latter, deriving from observation and experience in the vein of Newton, were accepted. The claim that the “project of Enlightenment” was to construct “master systems” (Siskin 2016) or that Spinoza was its “founder” (Israel 2001, 2006, 2012, 2019) thus seems untenable. As will be argued, Cassirer’s <em>Denkform </em>is a more viable analytical approach, albeit with certain modifications.