More and more often there appears, in lieu of the simple comprehension of the gross intake, a comprehension of the significances of the component sense-impressions, which have hardly been noticed as such before.[8] Finally these impressions themselves are discarded and replaced by the felt connotations of familiar word-sounds. The word, originally the name of a visual thing, changes imperceptibly into the label of a mental thing, the “concept.” We are far from being able to fix exact meanings to such names--that we can do only with wholly new names. We never use a word twice with identical connotation, and no one ever understands exactly as another does. But mutual comprehension is possible, in spite of this, because of the common world-outlook that has been induced in both, with and by the use of a common language; in an ambiance common to the lives and activities of both, mere word-sounds suffice to evoke cognate ideas. It is this mode of comprehending by means of sounds at once derived and detached (abstract) from actual seeing which, however rarely we can find it definitely evidenced at the primitive level, does in fact sharply separate the generic-animal kind of waking-consciousness from the purely human kind which supervenes. Just so, at an earlier stage, the appearance of waking-consciousness as such fixed a frontier between the general plantlike and the specifically animal existence. _Understanding detached from sensation is called thought._ Thought has introduced a permanent disunity into the human waking-consciousness. From early times it has rated understanding and sensibility as “higher” and “lower” soul-power. It has created the fateful opposition between the light-world of the eye, described as a figment and an illusion, and the world-imagined (“_vorgestellte_,” “set before” oneself), in which the concepts, with their faint but ineffaceable tinge of light-coloration, live and do business. And henceforth for man, so long as he “thinks,” this is the true world, the world-in-itself. At the outset the ego was waking-being as such (in so far, that is, as, having sight, it felt itself as the centre of a light-world); now it becomes “spirit”--namely, pure understanding, which “cognizes” itself as such and very soon comes to regard not only the world _around_ itself, but even the remaining component of life, its own body, as qualitatively _below itself_. This is evidenced not only in the upright carriage of man, but in the thoroughly intellectualized formation of his head, in which the eyes, the brow, and the temples become more and more the vehicles of expression.[9]