Consequentialist justifications of the state
Consequentialism in general, is a family of ethical philosophies that share this feature: human actions are to be evaluated by their effects upon other humans, or perhaps upon all other sentient creatures. Consequentialism opposes evaluation according to the motive of an action, for example, or according to whether that action complies with any conception of duty independent of consequences.
Consequentialism is sometimes confused with utilitarianism, but that is only one member of a broad family of theories that share the above-defined trait.
In law and political theory, a state or sovereign is an institution that legitimates a particular government. Sometimes arguments about legitimacy have a mystical side to them, as when kings claim divine right -- or when republics are explained on the basis of a hypothetical or primordial social contract.
But consequentialists spurn mystery. They might observe that the voters, as the state, create a government that then builds bridges, for example. They'll ask: would those bridges have been built in the absence of the state, and the government it sanctions? Are the bridges themselves valued by those who use them?
They'll reason that if the answer to the first question is negative and the second question is positive, no further justification of the state is required.
A philosopher who doubts or denies the legitimacy of the state might respond in any of several ways. He might, for example, question the ethical premise. He might say that the workers who built that bridge were exploited by the government that ordered it built, and by the investors in the private contractors who profitted, etc. He might have a deontological theory of exploitation, see deontology.
Alternatively, a skeptic might concede that the bridge is a good consequence but contend that even on consequentialist grounds the argument fails -- an even better bridge might have been built under anarcho-capitalist conditions -- see anarcho-capitalism. This counter-argument raises the issue of opportunity cost and the whole argument becomes an exercise in economic reasoning.