Naturally he makes mockery of the naturalists who “study natural history in their cabinets,” and would let his child Émile have “a cabinet much better furnished than that of crowned heads--the whole globe.” Teach the child with objects, by its own experience of them; never substitute the shadow unless where it is impossible to exhibit the substance; this is his general rule of instruction. The great psychological discovery proclaimed by Rousseau is that the child lives in a totally different world from that of grown-up people, that “childhood has its manner of seeing, perceiving, and thinking, peculiar to itself” (17: i, p. 108). He says: “We never know how to suppose ourselves in the place of children; we never enter into their manner of thinking. On the contrary, we attribute to them our ideas; and pursuing our own method of argumentation, fill their heads, even while we are discussing incontestable truths, with extravagance and error” (17: i, p. 268). No writer has ever before entered so deeply into the child-soul, and many facts first discovered by his wonderful power of observation are borne out by the more recent systematic studies. He is entitled to the name of the discoverer of childhood, and can be called the forerunner of child-study. Another great discovery made by Rousseau, which is related to the above, is that there are certain definite stages in the natural development of the child to which modes of education should correspond. True, Comenius divided the whole educative period, which, in his conception, covers the period of physical growth, into four, and assigned for each of them a different institution. But his gradation was made rather artificially and arbitrarily, while Rousseau’s division was based on his careful observation of the actual evolution of the child’s body and mind, the correctness of which is rather surprising in the light of modern science. The first epoch of human life begins with birth and ends with the time when the infant begins to eat and to walk. In this stage the principle of educating by inaction, on the part of the educator, by leaving the child to its natural development, is to be strictly observed. Absolute freedom should be granted to the child’s growing physical being. He also made a strong plea for the personal care of the child by the mother, which is said to have created a fashion among aristocratic mothers of the day, of carrying their nurslings even to balls and parties.