basis of pure right, so as at once to disprove his attack on society generally and to reinforce his criticism of existing societies. Round this point centres the whole dispute about the methods proper to political theory. There are, broadly speaking, two schools of political theorists, if we set aside the psychologists. One school, by collecting facts, aims at reaching broad generalisations about what actually happens in human societies! the other tries to penetrate to the universal principles at the root of all human combination. For the latter purpose facts may be useful, but in themselves they can prove nothing. The question is not one of fact, but one of right. Rousseau belongs essentially to this philosophical school. He is not, as his less philosophic critics seem to suppose, a purely abstract thinker generalising from imaginary historical instances; he is a concrete thinker trying to get beyond they inessential and changing to the permanent and invariable basis of human society. Like Green, he is in search of the principle of political obligation, and beside this quest all others fall into their place as secondary and derivative. It is required to find a form of association able to defend and protect with the whole common force the person and goods of every associate, and of such a nature, that each, uniting himself with all, may still obey only himself, and remain as free as before. This is the fundamental problem of which the _Social Contract_ provides the solution. The problem of political obligation is seen as including all other political problems, which fall into place in a system based upon it. How, Rousseau asks, can the will of the State help being for me a merely external will, imposing itself upon my own? How can the existence of the State be reconciled with human freedom? How can man, who is born free, rightly come to be everywhere in chains?