If we recall the context in which Locke was writing--the justification of King William's ascension to the throne and the Whig Revolution--another point that he makes in this section is clear. In the closing portion of Chapter 3, Locke notes that war results in the presence of corrupt of inept authority. Because of natural rights, people have the right to fight against a government that fails to represent their best interests. Sir Robert Filmer, whom Locke was specifically addressing, and Thomas Hobbes both make directly opposite claims. Filmer says that, because of the divine authority of kings, the people have no right to rebel against their sovereign. Hobbes says that, because people are so base and destructive, government must keep them in line by exerting absolute control. Locke argues that people have the right to respond to offensive incursions by unjust leadership as they would to offensive incursions by other people in the state of nature.
In Chapter 4, Locke defines social liberty as the agreement to live in a commonwealth under a central authority given a trust to act in the best interests of the commonwealth. Once again, we must examine word choice to better understand Locke's assumptions: the commonwealth is established "by consent," the legislative power can only act "according to the trust put in it."
After reading these first four chapters, we can start to understand Locke's ideas about human nature (as opposed to the state of nature). He appears to understand that people come into conflict with each other, steal from each other, are aggressive to each other, and so on. But he assumes also that people are rational enough to know their best interest. Unlike Hobbes, Locke does not believe that people must have power over themselves wrested from them in order to create functional societies. On the contrary, Locke sees personal liberty as the key component of a society that works toward the individual's and the commonwealth's best interest.