The whole history of the human mind, so far as we have any reliable history, is marked by this perpetual effort to find a First Cause. However wild and fantastic may be the idea which the savage conceives of a being stronger and wiser than himself; however groveling and sensual may be his conception of the form, or attributes, or action of that being, he is, when he strives after the comprehension of his deity, engaged in the same intellectual effort that is made by the most civilized and cultivated of mankind, when, speculating upon the origin of the human soul, or its relation to the universe, or the genesis of the material world, they reach the sublime conception of an infinite God, the creator of all other spiritual existences and of all the forms of animal life, or when they end in the theory that there is no God, or in that other theory which supposes that what we call the creation, man included, is an evolution out of primordial matter, which has been operated upon by certain fixed laws, without any special interposition of a creating power, exerted in the production of the forms of animal life that now inhabit this earth, or ever have inhabited it. In the investigation of these contrasted theories, it is necessary to remember that the faculties of the human mind are essentially the same in all conditions of civilization or barbarism; that they differ only in the degree of their growth, activity, and power of reasoning, and therefore that there must be a common standard to which to refer all beliefs. The sole standard to which we can refer a belief in anything is its rationality, or a comparison between that which is believed and that which is most probable, according to the power of human reason to weigh probabilities. In the untutored and uncultivated savage, this power, although it exists, is still very feeble; partly because it is exercised upon only a few objects, and partly because the individual has comparatively but little opportunity to know all the elements which should be taken into account in determining a question of moral probabilities.