From this proposition the historian concludes 'that the actions of men, being determined solely by their antecedents, must, under precisely the same circumstances, always issue in precisely the same results. And as all antecedents are either in the mind or out of it, we clearly see that all the variations in the results--in other words, all the changes of which history is full, all the vicissitudes of the human race, their progress or their decay, their happiness or their misery--must be the fruit of a double action; an action of external phenomena upon the mind, and another action of the mind upon the phenomena.' Mr. Buckle gives it as the result of his investigations concerning the relative influence of these two agencies: That external or physical laws have been most powerful in the earlier ages of the world, and among the most ignorant nations; that in proportion as knowledge increases, the power of this class of agencies diminishes, and that of mental laws becomes more predominant; that these latter are therefore the great motor forces of civilization, consisting of two parts, the moral and the intellectual, of which the latter are vastly superior as instruments of social advancement, stationary in their effects; finally, as the formal statement of the laws of human development, he says: '1st. That the progress of mankind depends on the success with which the laws of phenomena are investigated, and on the extent to which a knowledge of those laws is diffused. 2d. That before such investigation can begin, a spirit of scepticism must arise, which, at first aiding the investigation, is afterward aided by it. 3d. That the discoveries thus made increase the influence of intellectual truths, and diminish, relatively, not absolutely, the influence of moral truths; moral truths being more stationary than intellectual truths, and receiving fewer additions. 4th. That the great enemy of this movement, and therefore the great enemy of civilization, is the protective spirit--the notion that society cannot prosper, unless the affairs of life are watched over and protected at nearly every turn by the state and the church; the state teaching men what they are to do, and the church teaching them what they are to believe.' In all these points the recent work of Professor Draper coincides with that of the lamented English writer. The main object of the former is, however, to discuss a question more basic than those undertaken by the author of 'Civilization in England,' the consideration of which was by him formally declined: namely, the question of a predetermined order of development lying back of all physical and mental phenomena. The opening sentences of the American book will sufficiently indicate the purpose of its pages: