The State of Nature is a term in political philosophy used in social contract theories to describe the hypothetical condition that preceded governments. There must have been a time before government, and so the question is how legitimate government could emerge from such a starting position, and what are the hypothetical reasons for entering a state of society by establishing a government.
In some versions of social contract theory, there are no rights in the state of nature, only freedoms, and it is the contract that creates rights and obligations. In other versions the opposite occurs: the contract imposes restrictions upon individuals that curtail their natural rights.
Modern State of Nature Theories
The Hobbesean View
Thomas Hobbes argued that all humans are by nature equal in faculties of body and mind - in other words, no natural inequalities are so great as to give anyone a "claim" to an exclusive "benefit". From this equality and other causes in human nature, everyone is naturally willing to fight one another: so that "during the time men live without a common power to keep them all in awe, they are in that condition which is called war; and such a war as is of every man against every man". In this state every person has a natural right or liberty to do anything one thinks necessary for preserving one's own life; and life is "solitary, poor, nasty, brutish, and short" (Leviathan, Chapters XIII-XIV). Hobbes described this natural condition with the Latin phrase bellum omnium contra omnes (meaning war of all against all), in his De Cive. In Hobbes's view the state of nature exists at all times among independent countries, over whom there is no law except for those same precepts or laws of nature (Leviathan, Chapters XIII, XXX end). According to Hobbes, within the state of nature there is neither private property nor injustice since there is no law, except for certain natural precepts discovered by reason ("laws of nature"): the first of which is "that every man ought to endeavour peace, as far as he has hope of obtaining it" (Leviathan, Ch. XIV); and the second is "that a man be willing, when others are so too, as far forth as for peace and defence of himself he shall think it necessary, to lay down this right to all things; and be contented with so much liberty against other men as he would allow other men against himself". From here Hobbes develops the way out of the state of nature into political society and government, by mutual contracts - namely, between the subjects and their sovereign monarch, to whom all power is then ceded. Any rights that the subject then possesses (over and above their lives) are dispensed at the discretion of the Sovereign, who may arbitrarily withdraw them as seen fit.
An interesting point to note is that Thomas Hobbes was an atheist who also believed in absolute monarchy.
The Lockean View
John Locke claimed that the state of nature is one in which people have the freedom of acting out their lives and disposing of their own possessions as they think fit within the bounds of the "law of nature". In such a state, they need not ask permission to act nor depend on the will of others to arrange matters on their behalf. According to Locke, the natural state of human beings is also one of equality in which all power and jurisdiction is reciprocal and no one has more than another. He sees it as self-evident that all human beings (as creatures belonging to the same species and rank and born indiscriminately with all the same natural advantages and faculties) are equal among themselves in such a state.
However, while no individual in this state may tell another what to do or authoritatively pronounce justice in a given case, men are not actually allowed to do whatever they please. As expressed above, they must consult the dictates of the moral law of "doing unto others as you would have them do unto you" in regards to the freedom of others to act out their lives and dispose of their property. The specifics of this law are unwritten, however, and so each is likely to misapply it in his own case. In Locke's view, the social contract is entered into because the actual enjoyment of such rights is obviously uncertain in the state of nature, easily exposed to the forcible intrusions of others who misapply the moral law in their own cases (as is wont to happen); the actual social contract in Locke's view must be built on the union of people for the mutual preservation of their lives, liberty, and estate (what he would sum up as "property", drawing from the meaning of its Latin root proprius: what is one's own - including one's self).
In saying that political society was established for the better protection of property, Locke is claiming that it is to serve the private (non-political) interests of its constituent members. If it does not do this, it is to be deemed not a real social contract, being merely a false pretense at to prevent the idea that the intrusions of tyranny automatically return one to a state of nature in regards to the tyrant (whether that tyrant be an absolute monarch or the "general will" of social collective) from entering the common understanding (at least, in regards to the specific dictator at hand).
The Rousseauan View
Jean-Jacques Rousseau claimed that the state of nature was a primitive condition without law or morality, which human beings left for the benefits and necessity of cooperation. As society developed, division of labor and private property required the human race to adopt institutions of law. In the present degenerate phase of society, man is prone to be in frequent competition with his fellow men while also becoming increasingly dependent on them. This double pressure threatens both his survival and his freedom.
According to Rousseau, by joining together into civil society through the social contract and abandoning their claims of natural right, individuals can both preserve themselves and remain free. This is because submission to the authority of the general will of the people as a whole guarantees individuals against being subordinated to the wills of others and also ensures that they obey themselves because they are, collectively, the authors of the law. In Rousseau's social contract theory, a citizen cannot pursue his true interest by being an egoist but must instead subordinate himself to the law created by the citizenry acting as a collective.
Rousseau boldly claimed that man must "be forced to be free", understood in the following manner: since the indivisible and inalienable popular sovereignty decides what is good for the whole, then if an individual lapses back into his ordinary egoism and disobeys the leadership, he will be forced to listen to what they decided as a member of the collectivity (as citizens of the state). Thus, enforcement of law, including criminal law, is not a restriction on individual liberty, as the individual, as a citizen, explicitly agreed to be constrained if, as a private individual, he did not respect his own will as formulated in the general will. Because laws represent the restraints of civil freedom, they represent the leap made from humans in the state of nature into civil society. In this sense, the law is a civilizing force, and therefore Rousseau believed that the laws that govern a people helped to mold their character.