"The key," says Carus, "for the ascertainment of the nature of the conscious psychical life lies in the region of the unconscious(71)." The view which these words take is at least as old as the days of Leibniz. It means that the mental world does not abruptly emerge a full-grown intelligence, but has a genesis, and follows a law of development: that its life may be described as the differentiation (with integration) of a simple or indifferentiated mass. The terms conscious and unconscious, indeed, with their lax popular uses, leave the door wide open for misconception. But they may serve to mark that the mind is to be understood only in a certain relation (partly of antithesis) to nature, and the soul only in reference to the body. The so-called "superior faculties"--specially characteristic of humanity--are founded upon, and do not abruptly supersede, the lower powers which are supposed to be specially obvious in the animals(72). The individual and specific phenomena of consciousness, which the psychologist is generally supposed to study, rest upon a deeper, less explicated, more indefinite, life of sensibility, which in its turn fades away by immeasurable gradations into something irresponsive to the ordinary tests for sensation and life.
And yet the moment we attempt to leave the daylight of consciousness for the darker sides of sub-conscious life, the risks of misinterpretation multiply. The problem is to some extent the same as confronts the student of the ideas and principles of primitive races. There, the temptation of seeing things through the "spectacles of civilisation" is almost irresistible. So in psychology we are apt to import into the life of sensation and feeling the distinctions and relations of subsequent intellection. Nor is the difficulty lessened by Hegel's method which deals with soul, sentiency, and consciousness as grades or general characteristics in a developmental advance. He borrows his illustrations from many quarters, from morbid and anomalous states of consciousness,--less from the cases of savages, children and animals. These illustrations may be called a loose induction. But it requires a much more powerful instrument than mere induction to build up a scientific system; a framework of general principle or theory is the only basis on which to build theory by the allegation of facts, however numerous. Yet in philosophic science, which is systematised knowledge, all facts strictly so described will find their place and be estimated at their proper value.