By stripping this Being, so constituted, of all the supernatural gifts he may have received, and of all the artificial faculties he could have only acquired by prolonged progress; by considering him, in a word, such as he must have issued from the hands of Nature, I see an animal less strong than some, less agile than others, but, all things considered, the most advantageously organized of all
This is a clear statement of Rousseau's methodology, and of the most startling assumption that he makes in the work. The "Supernatural gifts" and "artificial faculties" are language, sociability and reason, which for Rousseau emerge after a long process of development. Man as created was nothing more than an animal. This may not sound particularly shocking to modern readers, who are familiar with the theory of evolution, but it sounded more radical in the eighteenth century. A long tradition of writers considered man as created especially by God, to rule over the animals, from whom he was distinguished by reason. Reason is in many ways the defining human characteristic for these writers, but Rousseau discards it entirely. What makes humans human initially is their "organization," or their physical structure. Their perfectibility means that they have an in-built advantage over other animals, but there is no reason why they must or should develop into rational beings. In many ways, Rousseau states the presumptions of evolutionary theory many years before Darwin.