Complex sentence: Like John Locke, who believed that a government can only be legitimate if it has been sanctioned by the people in the role of the sovereign, Rousseau claimed that a perfect society would be controlled by the "general will" of its populace.
Split into simpler sentences: Like John Locke, Rousseau believed that a government can only be legitimate if it has been sanctioned by the people in the role of the sovereign. In addition, Rousseau maintained that a perfect society would be controlled by the "general will" of its populace.