John Locke, On the Origin of Government
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 by which 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 or 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 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.
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....
And therefore we see that in assemblies empowered to act by positive laws, where no number is set by that positive law which empowers them, the act of the majority passes for the act of the whole, and of course determines, as having by the law of nature and reason the power of the whole.
And thus every man, by consenting with others to make one body politic under one government, puts himself under an obligation to every one of that society, to submit to the determination of the majority, and to be concluded by it; or else this original compact, whereby he with others incorporates into one society, would signify nothing, and be no compact, if he be left free and under no other ties than he was in before in the state of nature. For what appearance would there be of any compact? What new engagement if he were no farther tied by any decrees of the society, than he himself thought fit, and did actually consent to? This would be still as great a liberty as he himself had before his compact, or any one else in the state of nature hath, who may submit himself and consent to any acts of it if he thinks fit....
Whosoever therefore out of a state of nature unite into a community must be understood to give up all the power necessary to the ends for which they unite into society, to the majority of the community, unless they expressly agreed in any number greater than the majority. And this is done by barely agreeing to unite into one political society, which is all the compact that is, or needs be, between the individuals that enter into make up a commonwealth. And thus that which begins and actually constitutes any political society is nothing but the consent of any number of freemen capable of a majority to unite and incorporate into such a society. And this is that, and that only, which did or could give beginning to any lawful government in the world....
From John Locke, Second Treatise on Government in Sources of British Political Thought, edited by Wilfrid Harrison. (New York: Macmillan, 1965), pp. 55-57.
For more on Locke take a look at the following links:
Biography of Locke -http://www.rjgeib.com/thoughts/constitution/locke-bio.html
Another biography of Locke with links to his works -http://thor.pcc.edu/~ap-sec/jlocke.htm
Essay Concerning Human Understanding -http://www.systems.org/HTML/books/j-locke.htm