Strictly speaking, there is only one internal principle of progress, namely, _rationality_. By rationality, in this connection, I mean the knowledge of the good, and the correction of existing usages through which it is accidentally or wantonly frustrated. If fulfilment be the motive of life, and maximum fulfilment be the good, then any existing usage stands condemned when it is proved to involve unnecessary sacrifice. And such usages will be condemned, and in the long run rejected, wherever there is an opportunity for self-assertion and discussion among the various interests concerned. But such correction may be initiated either by a positive or a negative motive. It may result either from the action of those who seek constructively to promote the general welfare of society, or from the action of those who protest against society in behalf of neglected interests. The first is _constructive reform_, the second, _revolution_. _Constructive reform_ is the work of disinterested {135} reflection. It may originate in speculation, as political or social theory; or it may originate in the solution of a practical problem. Plato has described the type of mind which in either case it requires: a mind which is free from individual or party bias, and which represents and co-ordinates all the interests of the community. Now the failure of political and social theories as measures of reform is proverbial; none failed more completely and conspicuously than Plato's own. And it is not difficult to see why this should be the case; for, as a rule, they are adapted neither to the habits and intelligence of the time, nor to the actual instruments of practical efficiency. But it may be observed that the distance between the philosopher and the man of affairs is considerably shorter than it used to be. The method of discussion being once generally adopted, action, both individual and social, is pervaded with theory. Even the man of affairs cannot easily avoid being a philosopher. And even in distinguishing as sharply as I have between theory and practice, I have simply followed a customary habit of thought that is on the whole misleading. For, in truth, it is as impossible for the man of affairs to avoid disinterested reflection, as it is for the commercial traveller to be unsociable. The activity of the one has to do with the organization of a wide range of {136} interests, as the activity of the other has to do with the capitalization of good-fellowship.