Jean Jacques Rousseau (1712–1778). Social Contract & Discourses. 1913.The Social Contract or Principles of Political Right. Book III.
Chapter X. The Abuse of Government and Its Tendency to Degenerate
There are two general courses by which government degenerates: i. e. when it undergoes contraction, or when the State is dissolved.
Government undergoes contraction when it passes from the many to the few, that is, from democracy to aristocracy, and from aristocracy to royalty. To do so is its natural propensity. If it took the backward course from the few to the many, it could be said that it was relaxed; by this inverse sequence is impossible.
Indeed, governments never change their form except when their energy is exhausted and leaves them too weak to keep what they have. If a government at once extended its sphere and relaxed its stringency, its force would become absolutely nil, and it would persist still less. It is therefore necessary to wind up the spring and tighten the hold as it gives way: or else the State it sustains will come to grief.
The dissolution of the State may come about in either of two ways.
First, when the prince ceases to administer the State in accordance with the laws, and usurps the Sovereign power. A remarkable change then occurs: not the government, but the State, undergoes contraction; I mean that the great State is dissolved, and another is formed within it, composed solely of the members of the government, which becomes for the rest of the people merely master and tyrant. So that the moment the government usurps the Sovereignty, the social compact is broken, and all private citizens recover by right their natural liberty, and are forced, but not bound, to obey.
The same thing happens when the members of the government severally usurp the power they should exercise only as a body; this is as great an infraction of the laws, and results in even greater disorders. There are then, so to speak, as many princes as there are magistrates, and the State, no less divided than the government, either perishes or changes its form.
When the State is dissolved, the abuse of government, whatever it is, bears the common name of anarchy. To distinguish, democracy degenerates into ochlocracy, and aristocracy into oligarchy; and I would add that royalty degenerates into tyranny; but this last word is ambiguous and needs explanation.
In vulgar usage, a tyrant is a king who governs violently and without regard for justice and law. In the exact sense, a tyrant is an individual who arrogates to himself the royal authority without having a right to it. This is how the Greeks understood the word “tyrant”: they applied it indifferently to good and bad princes whose authority was not legitimate. Tyrant and usurper are thus perfectly synonymous terms.
In order that I may give different things different names, I call him who usurps the royal authority a tyrant, and him who usurps the sovereign power a despot. The tyrant is he who thrusts himself in contrary to the laws to govern in accordance with the laws; the despot is he who sets himself above the laws themselves. Thus the tyrant cannot be a despot, but the despot is always a tyrant.