Excerpt from Rousseau's "Social Contract"

As soon as this multitude is so united in one body, it is impossible to offend against one of the members without attacking the body, and still more to offend against the body without the members resenting it. Duty and interest therefore equally oblige the two contracting parties to give each other help; and the same men should seek to combine, in their double capacity, all the advantages dependent upon that capacity.

Again, the Sovereign, being formed wholly of the individuals who compose it, neither has nor can have any interest contrary to theirs; and consequently the sovereign power need give no guarantee to its subjects, because it is impossible for the body to wish to hurt all its members. We shall also see later on that it cannot hurt any in particular. The Sovereign, merely by virtue of what it is, is always what it should be.

This, however, is not the case with the relation of the subjects to the Sovereign, which, despite the common interest, would have no security that they would fulfil their undertakings, unless it found means to assure itself of their fidelity.

In fact, each individual, as a man, may have a particular will contrary or dissimilar to the general will which he has as a citizen. His particular interest may speak to him quite differently from the common interest: his absolute and naturally independent existence may make him look upon what he owes to the common cause as a gratuitous contribution, the loss of which will do less harm to others than the payment of it is burdensome to himself; and, regarding the moral person which constitutes the State as a persona ficta, because not a man, he may wish to enjoy the rights of citizenship without being ready to fulfil the duties of a subject. The continuance of such an injustice could not but prove the undoing of the body politic.

In order then that the social compact may not be an empty formula, it tacitly includes the undertaking, which alone can give force to the rest, that whoever refuses to obey the general will shall be compelled to do so by the whole body. This means nothing less than that he will be forced to be free; for this is the condition which, by giving each citizen to his country, secures him against all personal dependence. In this lies the key to the working of the political machine; this alone legitimises civil undertakings, which, without it, would be absurd, tyrannical, and liable to the most frightful abuses.