This complex idea of a personal world, of personality, which constantly increases in content, is given a special name, John or Mary, and still later another name, _I_. The unity of the idea of personality, the readiness of its appearance in consciousness in spite of the multitude of its contents, is greatly enhanced by this name. The idea _I_ becomes the omnipresent and dominating factor in consciousness. I can see nothing, hear nothing, imagine nothing without, however vaguely, thinking that it is _I_ who reads, _I_ who answers, _I_ who designs. It is altogether impossible to express such thoughts in language without reference to the _I_ or the _mine_. In the ecstasy of the mystic or the mental exaltation of the insane, the idea of _I_ may be absent, but never under normal conditions at an age beyond that of infancy. Consciousness in which the idea of _I_ is rather pronounced is commonly called self-consciousness. It is plain enough that thinking of the other half of the world, other than the self, is also facilitated by such names as “the world,” “the external world.” But the concept of the external world does not easily attain the unity of the concept of self, because the experiences referred to are too changeable in comparison with those referred to by _I_. We speak of the external world chiefly in order to distinguish it from the self, not because of the unity of its conception. The extraordinary support which the consciousness of self receives from language has had also a certain undesirable consequence. We have mentioned in an earlier chapter the universal desire to imagine the world as being under the power of innumerable demons. The consciousness of the self thus leads naturally to the thought of a demon who inhabits the human body. When a person under ordinary conditions is conscious of the _I_, there is no time for its content to unfold itself to any considerable extent. Usually one small group of ideas enters consciousness, even when I ask myself the question as to what I am: ideas of a certain visual appearance, a certain position in society, a certain age, certain aims in life. It seems then that the concept of self is exceedingly simple. This apparent simplicity gives aid to the idea of the existence of a simple demon, independent of time, eternal, inhabiting and governing this body as long as its organs are held together by their normal physiological functions, after the body’s death going elsewhere--whither, we do not know. But this conclusion as to the existence of a simple, unitary subjective reality is no more justifiable than the statement that, because of the simplicity of the idea _it_ in ordinary language, there must be an absolutely simple objective reality which corresponds to it.