Rousseau is careful to separate the government from the sovereign. The sovereign — the people acting collectively — holds the legislative power. The government is a subordinate body whose role is merely to execute the laws. Governments can be structured in many ways, but they are always the servant of the sovereign people, not its master. The moment government ceases to serve the general will, it becomes tyrannical.
Rousseau examines the three classical forms: democracy (the people govern directly), aristocracy (a smaller group governs), and monarchy (one person governs). He is sceptical of strict democracy — it requires a level of civic virtue and scale of society rarely achieved. A small aristocracy of talent is often the most practical form of government for a mid-sized state. Monarchy concentrates will and force, but is prone to corruption and succession crises.
All governments have a natural tendency to degenerate — to contract their power and serve the rulers' interests rather than the common good. Democracy slides into ochlocracy, aristocracy into oligarchy, monarchy into tyranny. The only remedy is the periodic reassertion of popular sovereignty: the people must always retain the right to reconvene, revoke the government, and reconstitute its own political order. No constitutional arrangement is final.
Forms of government are analysed in Book III of The Social Contract (1762). G.D.H. Cole translation, 1913.
