These non-progressive purposes in which mental power is consumed may be classified as maintenance and conflict. By maintenance I mean, not only the support of existence, but the keeping up of the social condition and the holding of advances already gained. By conflict I mean not merely warfare and preparation for warfare, but all expenditure of mental power in seeking the gratification of desire at the expense of others, and in resistance to such aggression. To compare society to a boat. Her progress through the water will not depend upon the exertion of her crew, but upon the exertion devoted to propelling her. This will be lessened by any expenditure of force required for bailing, or any expenditure of force in fighting among themselves, or in pulling in different directions. Now, as in a separated state the whole powers of man are required to maintain existence, and mental power is set free for higher uses only by the association of men in communities, which permits the division of labor and all the economies which come with the co-operation of, increased numbers, association is the first essential of progress. Improvement becomes possible as men come together in peaceful association, and the wider and closer the association, the greater the possibilities of improvement. And as the wasteful expenditure of mental power in conflict becomes greater or less as the moral law which accords to each an equality of rights is ignored or is recognized, equality (or justice) is the second essential of progress. Thus association in equality is the law of progress. Association frees mental power for expenditure in improvement, and equality, or justice, or freedom--for the terms here signify the same thing, the recognition of the moral law--prevents the dissipation of this power in fruitless struggles. Here is the law of progress, which will explain all diversities, all advances, all halts, and retrogressions. Men tend to progress just as they come closer together, and by co-operation with each other increase the mental power that may be devoted to improvement; but just as conflict is provoked, or association develops inequality of condition and power, this tendency to progression is lessened, checked, and finally reversed. Given the same innate capacity, and it is evident that social development will go on faster or slower, will stop or turn back, according to the resistances it meets. In a general way these obstacles to improvement may, in relation to the society itself, be classed as external and internal--the first operating with greater force in the earlier stages of civilization, the latter becoming more important in the later stages.