The purpose, or end, of government is to secure the equal natural rights of the people on the basis of consent. Governments derive their “just powers” from the consent of the governed. “Consent” is the means by which government secures its purpose of protecting rights. But why must there be consent?
Consent is necessary because “all men are created equal.” If all men are not created equal, then just government does not require consent. You could rightly rule human beings like you would rule a dog or a horse. But if it is true that all men are created equal, then no man can rightly rule another man without that latter’s consent.