That we may rightly appreciate what this Monism is, let us now, from a philosophico-historical point of view cast a comprehensive glance over the development in time of man's knowledge of nature. A long series of varied conceptions and stages of human culture here passes before our mental vision. At the lowest stage, the rude--we may say animal--phase of prehistoric primitive man, is the "ape-man," who, in the course of the tertiary period, has only to a limited degree raised himself above his immediate pithecoid ancestors, the anthropoid apes. Next come successive stages of the lowest and simplest kind of culture, such as only the rudest of still existing primitive peoples enable us in some measure to conceive. These "savages" are succeeded by peoples of a low civilisation, and from these again, by a long series of intermediate steps, we rise little by little to the more highly civilised nations. To these alone--of the twelve races of mankind only to the Mediterranean and Mongolian--are we indebted for what is usually called "universal history." This last, extending over somewhat less than six thousand years, represents a period of infinitesimal duration in the long millions of years of the organic world's development. Neither of the primitive men we have spoken of, nor of those who immediately succeeded them, can we rightly predicate any knowledge of nature. The rude primitive child of nature at this lowest stage of development is as yet far from being the restless _Ursachenthier_ (cause-seeking animal) of Lichtenberg; his demand for causes has not yet risen above that of apes and dogs; his curiosity has not yet mounted to pure desire of knowledge. If we must speak of "reason" in connection with pithecoid primitive man, it can only be in the same sense as that in which we use the expression with reference to those other most highly developed Mammals, and the same remark holds true of the first beginnings of religion.[3] It is indeed still not infrequently the custom to deny absolutely to the lower animals reason and religion. An unprejudiced comparison, however, convinces us that this is wrong. The slow and gradual process towards completeness which, in the course of thousands of years, civilised life has been working in the soul of man, has not passed away without leaving some trace on the soul of our highest domestic animals also (above all, of dogs and horses). Constant association with man, and the steady influence of his training, have gradually, and by heredity, developed in their brain higher associations of ideas and a more perfect judgment. Drill has become instinct, an undeniable example of "the transmission of acquired characters."[4]