Men are not swayed exclusively by considerations of material self-interest, as the older school of economists generally assumed; nor even by spiritual self-interest, as too much of the religious teaching of the past has assumed; nor even by consideration of the welfare of the social groups of which they are members. Many of the great events of history have been determined by ideas that have had no relation to individual welfare, but have inspired a collective enthusiasm for collective action, for national effort, of a disinterested kind; and the lives of some nations have been dominated by some one or two such ideas. These ideas are first conceived and taught by some great man, or by a few men who have acquired prestige and influence; they then become generally accepted by suggestion and imitation, accepted more or less uncritically and established beyond the reach of argument and reasoning. No matter what the character of the idea, its collective acceptance by a people enhances for the time the homogeneity of mind among them, renders the people more intimately a unity, and serves also to mark it off more sharply from other peoples among whom other ideas prevail. But, besides thus binding together at any period of its history the people that entertains it the generally accepted idea, if it endures, may produce further effects by becoming incorporated in the national organisation; in so far as it determines the form of activity of the people, it moulds their institutions and customs into harmony with itself, until they become in some measure its embodiment and expression; and in any vigorous nation there are usually one or two dominant ideas at work in this way. It is a favourite dogma with some writers (for example M. le Bon) that ideas, before they can exert great effects in the life of a nation, must first become unconscious ideas, incorporated as they say in the unconscious soul of a people. This is an obscure confused doctrine, which, if it is meant to be taken literally, we can only reject. If it is to have any real meaning, it must be taken in the sense that the long prevalence of the ideal moulds the institutions and customs and the executive organisation of a people, so that national action towards the ideal end becomes more or less automatic or routine. If the ideal so accepted and incorporated in the organised structure of the national mind, is one that makes for strength and at the same time permits of progress, it lives on; in other cases it may destroy the nation, or petrify it, arresting all progress.