sensations
Rousseau is evoking the epistemological assumptions of Locke, who in his Essay Concerning Human Understanding developed a sensationalist psychology whose roots may be found in Hobbes'Leviathan, Part I, "Of Man," chaps 1-6. In 1754 Rousseau's contemporary and friend the Abbé de Condillac had written aTreatise on the Sensations popularizing Locke's views.