A.K.A. The sceptic's guide to political authority; or, why unanimous direct democracy is the only solution.
This is a book that questions the possibility of political philosophy (understood as "The discovery, analysis, and demonstration of the forms and principles of legitimate authority--of the right to rule" (p.5)) by questioning the legitimacy of its central concept; that is, the normative concept of state, understood as "the group of persons who have the right to exercise supreme authority [i.e., the right to command and correlatively the right to be obeyed] within a territory" (ibid.).
The legitimacy question asks for the conditions under which a state (or supreme authority) can rightly exist, and the reasons for this; supreme authority being a nonempirical normative concept, the only way we can know whether it is legitimate is by making an a priori argument that shows that there can be forms of human community in which one (or some) men have a moral right to rule (p.8). Correlatively, this can be understood as a quest for an argument that shows that we have a moral obligation to obey commands by the state.
Now Wolff presents a single crucial second element here: as rational beings who are responsible for their actions (therefore, metaphysically free), humans have an obligation to be morally autonomous; that is, they have an obligation to rationally deliberate and decide by and for themselves what they should do, and only bind themselves to laws that they have legislated for themselves (that is the meaning of being autonomous, according to Wolff -- see p.14). What is implied by this is that, as long as someone strives to be autonomous, they will never obey any commands because they are told to do so: the autonomous man recognizes no authority or will over him (of course, he can come up with his own reasons for doing what he is told to do, but as long as those reasons come out of his own will and deliberation, it will be an autonomous decision).
By combining the absolute authority essential to the normative concept of state and the moral obligation to be autonomous, we arrive at what is considered by Wolff to be the fundamental problem of political philosophy: The conflict of authority and autonomy.
If every conceivable de jure state has by conceptual entailment supreme authority, and everyone has an obligation to be autonomous (and this in itself implies that no one should obey commands or laws because they are told to do so), then everyone must reject the state's claim of authority over them if they strive to achieve autonomy. In other words, if there's moral obligation to be achieve autonomy at whatever cost, there are no states whose subjects have a moral obligation to obey its commands: no state is legitimate, and the only viable option available to the autonomous man is philosophical anarchism (p.18).
It should be noted that this by itself doesn't mean that one should abolish the state, or that every state is unworthy of support: Wolff clearly recognizes this when he says the we can engage in prudential reasonings to obey various state laws (maybe by self-interest or any other kind of reasoining of the sort); the only thing the autonomous man is obliged to is to never obey an external law simply because it is the law: again, the decision must come from his own will and reasons.
It should also be noted that this problem is supported by very controversial assumptions, that should not be taken as truths at face-value, I believe: that every agent is essentially (i.e., analitically) autonomous; that autonomy conceptually precludes any kind of authority; that "state" is a concept that can be clearly defined (therefore with clearly identifiable essential properties), etc. So Wolff's argument is not trivial at all, and should analysed carefully.
The rest of the book proceeds to analyse various alternative solutions to the problem of authority and autonomy. Wolff believes the solution lies in democracy, since in it every man is a law-giver and a law-obeyer, and therefore men can collectively bind themselves to laws collectively made by themselves (p.21-2). More precisely, the only form of democracy that constitutes a genuine solution is unanimous direct democracy, under which "every member of society wills freely every law which is actually passed", thus allowing authority and autonomy to coexist harmoniously (and this does not require that men have equal desires or reasons -- in fact, there can be disagreement in those departments). Therefore, unanimous direct democracy is the only condition for a legitimate state (I even wonder why Wolff bothered to call this a defense of anarchism in the first place, since he just demonstrated the legitimacy of the normative concept of state -- go figure). For reasons I won't develop here, Wolff rejects other forms of democracy as genuine solutions to the problem, whether it be representative ones founded on contractual promises, or majoritarian ones. I personally find this section to be of great use if one wants to question standard conceptions of democracy.
Leaving unanimous direct democracy aside, if there's no way to resolve the conflict between authority and autonomy, we're left with a dilemma: either we treat all existing states as illegitimate and only obey their commands after careful evaluation, or we give up autonomy altogether and stick to whatever form of government we think is the most beneficial or just to us; and, if we do that, then we'll have no moral reason to prefer democracy to any other beneficial form of government, such as benevolent dictatures or monarchies. Wolff thinks that giving up autonomy is completely out of the question, but doesn't seem very satisfied with the anarchist conclusion (What is your choice?). Lastly, Wolff sketches out a (not very detailed) model of anarchist society that could preserve a reasonable degree of social coordination as part of a positive anarchist project, though recognizing it as a massively underdeveloped part of the project.
Overall, I'm very impressed by the book, and I enjoyed almost every single page of it; I would easily read all of it again, and even use it for didactic purposes. Wolff's style is clear and engaging, the problem, solutions and discussion he presents are stimulating, and his arguments are also pretty interesting in themselves. I recommend this to anyone interested in the problem of authority; you will most likely not be disappointed.