Philosophy
Hobbes builds political authority from fear, conflict, obligation and the need for a power capable of securing peace.
Whenever people live without a shared power that keeps them all in awe, they are already in a state of war, even if no fighting is happening at the moment. War here means a standing condition of mutual threat, not only actual battles. Every person counts as a potential enemy to every other.
When people can rely only on their own strength and cleverness for safety, nobody plants, builds, trades, studies or writes. The rewards of that work are too uncertain to be worth the effort. Life without a common protector is therefore not just dangerous but poor and empty: "solitary, poore, nasty, brutish, and short."
A state does not arise naturally. It is brought into being by the pacts and covenants that people make with one another. Hobbes compares these founding agreements to the words by which God created the first man: the act of agreeing is what gives the body politic its existence.
A country can be torn apart when one side claims too much for liberty and the other claims too much for authority. Ambitious leaders then recruit the envy and resentment of an excitable public to advance their own goals. Hobbes wrote his case for strong authority out of grief at seeing this happen.
People are pushed by their own appetites and above all by fear of a violent death. Hobbes argues that this fear, more than any natural love of company, is what leads people to accept a ruler. Political order is built on top of that fear rather than on human goodwill.
Hobbes rejects the old view that people are born to live together in communities. On his account human nature is competitive and self-seeking, so society does not grow on its own. It has to be deliberately built and held together.
Hobbes argues that people are better off giving up the unlimited but anarchic freedom they would have with no ruler in exchange for protection and enforced law. The bargain is security in place of liberty. He presents this as the rational choice, though his critics, then and since, have contested it.
The commonwealth is a man-made creature, a great "Leviathan" assembled out of its members. Hobbes treats life as nothing more than motion, so a built mechanism can count as alive in the same sense. On that view the state is a constructed body that can be designed and analysed like a machine.
Hobbes argues that only a strong, absolute sovereign can stop civil war and chaos. To do so it must hold both worldly and religious authority, because any rival centre of power gives factions something to fight over. Contemporaries found this so dangerous that the book was burnt for sedition.