Three Social Contract Theories:

Hobbes, Locke, Rousseau

Hobbes, Leviathan, chapter 17:

The only way [emphasis added] to erect such a common power, as may be able to defend them from the invasion of foreigners, and the injuries of one another, and thereby to secure them in such sort as that by their own industry and by the fruits of the earth they may nourish themselves and live contentedly, is to confer all their power and strength upon one man, or upon one assembly of men, that may reduce all their wills, by plurality of voices, unto one will: which is as much as to say, to appoint one man, or assembly of men, to bear their person; and every one to own and acknowledge himself to be author of whatsoever he that so beareth their person shall act, or cause to be acted, in those things which concern the common peace and safety; and therein to submit their wills, everyone to his will, and their judgements to his judgement. This is more than consent, or concord; it is a real unity of them all in one and the same person, made by covenant of every man with every man, in such manner as if every man should say to every man: I authorize and give up my right of governing myself to this man, or to this assembly of men, on this condition; that thou give up, thy right to him, and authorize all his actions in like manner. This done, the multitude so united in one person is called a COMMONWEALTH; in Latin, CIVITAS. This is the generation of that great LEVIATHAN, or rather, to speak more reverently, of that mortal god to which we owe, under the immortal God, our peace and defense. For by this authority, given him by every particular man in the Commonwealth, he hath the use of so much power and strength conferred on him that, by terror thereof, he is enabled to form the wills of them all, to peace at home, and mutual aid against their enemies abroad. And in him consisteth the essence of the Commonwealth; which, to define it, is: one person, of whose acts a great multitude, by mutual covenants one with another, have made themselves every one the author, to the end he may use the strength and means of them all as he shall think expedient for their peace and common defense.

Locke, Second Treatise of Government, section 87:

Section 87. Man being born, as has been proved, with a title to perfect freedom, and an uncontrolled enjoyment of all the rights and privileges of the law of nature, equally with any other man, or number of men in the world, hath by nature a power, not only to preserve his property, that is, his life, liberty and estate, against the injuries and attempts of other men; but to judge of, and punish the breaches of that law in others, as he is persuaded the offence deserves, even with death itself, in crimes where the heinousness of the fact, in his opinion, requires it. But because no political society can be, nor subsist, without having in itself the power to preserve the property, and in order thereunto, punish the offences of all those of that society; there, and there only [emphasis added] is political society, where every one of the members hath quitted this natural power, resigned it up into the hands of the community in all cases that exclude him not from appealing for protection to the law established by it. And thus all private judgment of every particular member being excluded, the community comes to be umpire, by settled standing rules, indifferent, and the same to all parties; and by men having authority from the community, for the execution of those rules, decides all the differences that may happen between any members of that society concerning any matter of right; and punishes those offences which any member hath committed against the society, with such penalties as the law has established: whereby it is easy to discern, who are, and who are not, in political society together. Those who are united into one body, and have a common established law and judicature to appeal to, with authority to decide controversies between them, and punish offenders, are in civil society one with another: but those who have no such common appeal, I mean on earth, are still in the state of nature, each being, where there is no other, judge for himself, and executioner; which is, as I have before shewed it, the perfect state of nature.

Sections 95 and 96 (partial):

Section 95. MEN being, as has been said, by nature, all free, equal, and independent, no one can be put out of this estate, and subjected to the political power of another, without his own consent. The only way [emphasis added] whereby any one divests himself of his natural liberty, and puts on the bonds of civil society, is by agreeing with other men to join and unite into a community for their comfortable, safe, and peaceable living one amongst another, in a secure enjoyment of their properties, and a greater security against any, that are not of it. This any number of men may do, because it injures not the freedom of the rest; they are left as they were in the liberty of the state of nature. When any number of men have so consented to make one community or government, they are thereby presently incorporated, and make one body politic, wherein the majority have a right to act and conclude the rest.

Section 96. For when any number of men have, by the consent of every individual, made a community, they have thereby made that community one body, with a power to act as one body, which is only by the will and determination of the majority: for that which acts any community, being only the consent of the individuals of it, and it being necessary to that which is one body to move one way; it is necessary the body should move that way whither the greater force carries it, which is the consent of the majority: or else it is impossible it should act or continue one body, one community, which the consent of every individual that united into it, agreed that it should; and so every one is bound by that consent to be concluded by the majority. . . .

Rousseau, The Social Contract, Book One, chapter 6:

Chapter 6. The Social Compact

I SUPPOSE men to have reached the point at which the obstacles in the way of their preservation in the state of nature show their power of resistance to be greater than the resources at the disposal of each individual for his maintenance in that state. That primitive condition can then subsist no longer; and the human race would perish unless it changed its manner of existence.

But, as men cannot engender new forces, but only unite and direct existing ones, they have no other means of preserving themselves than the formation, by aggregation, of a sum of forces great enough to overcome the resistance. These they have to bring into play by means of a single motive power, and cause to act in concert.

 This sum of forces can arise only where several persons come together: but, as the force and liberty of each man are the chief instruments of his self-preservation, how can he pledge them without harming his own interests, and neglecting the care he owes to himself? This difficulty, in its bearing on my present subject, may be stated in the following terms:

"The problem is to find a form of association which will defend and protect with the whole common force the person and goods of each associate, and in which each, while uniting himself with all, may still obey himself alone, and remain as free as before." This is the fundamental problem of which the Social Contract provides the solution. 

The clauses of this contract are so determined by the nature of the act that the slightest modification would make them vain and ineffective [emphasis added]; so that, although they have perhaps never been formally set forth, they are everywhere the same and everywhere tacitly admitted and recognised, until, on the violation of the social compact, each regains his original rights and resumes his natural liberty, while losing the conventional liberty in favour of which he renounced it. 

These clauses, properly understood, may be reduced to one — the total alienation of each associate, together with all his rights, to the whole community; for, in the first place, as each gives himself absolutely, the conditions are the same for all; and, this being so, no one has any interest in making them burdensome to others.

Moreover, the alienation being without reserve, the union is as perfect as it can be, and no associate has anything more to demand: for, if the individuals retained certain rights, as there would be no common superior to decide between them and the public, each, being on one point his own judge, would ask to be so on all; the state of nature would thus continue, and the association would necessarily become inoperative or tyrannical.

 Finally, each man, in giving himself to all, gives himself to nobody; and as there is no associate over whom he does not acquire the same right as he yields others over himself, he gains an equivalent for everything he loses, and an increase of force for the preservation of what he has.

 If then we discard from the social compact what is not of its essence, we shall find that it reduces itself to the following terms:

"Each of us puts his person and all his power in common under the supreme direction of the general will, and, in our corporate capacity, we receive each member as an indivisible part of the whole."

At once, in place of the individual personality of each contracting party, this act of association creates a moral and collective body, composed of as many members as the assembly contains votes, and receiving from this act its unity, its common identity, its life and its will. This public person, so formed by the union of all other persons formerly took the name of city,⁴ and now takes that of Republic or body politic; it is called by its members State when passive. Sovereign when active, and Power when compared with others like itself. Those who are associated in it take collectively the name of people, and severally are called citizens, as sharing in the sovereign power, and subjects, as being under the laws of the State. But these terms are often confused and taken one for another: it is enough to know how to distinguish them when they are being used with precision.