The faculty of speech makes society possible--nothing more.
Not without interest do we remark the progress of development of this function.

The invention of the art of writing gave extension and durability to the registration or record of impressions.

These, which had hitherto been stored up in the brain of one man, might now be imparted to the whole human race, and be made to endure forever.
Civilization became possible--for civilization cannot exist without writing, or the means of record in some shape.
From this psychological point of view we perceive the real significance of the invention of printing--a development of writing which, by increasing the rapidity of the diffusion of ideas, and insuring their permanence, tends to promote civilization and to unify the human race.
In the foregoing paragraphs, relating to nervous impressions, their registry, and the consequences, that spring from them, I have given an abstract of views presented in my work on "Human Physiology," published in 1856, and may, therefore, refer the reader to the chapter on "Inverse Vision, or Cerebral Sight;" to Chapter XIV., Book I.; and to Chapter VIII., Book II.; of that work, for other particulars.
The only path to scientific human psychology is through comparative psychology.

It is a long and wearisome path, but it leads to truth.
Is there, then, a vast spiritual existence pervading the universe, even as there is a vast existence of matter pervading it--a spirit which, as a great German author tells us, "sleeps in the stone, dreams in the animal, awakes in man ?" Does the soul arise from the one as the body arises from the other?
Do they in like manner return, each to the source from which it has come?
If so, we can interpret human existence, and our ideas may still be in unison with scientific truth, and in accord with our conception of the stability, the unchangeability of the universe.
To this spiritual existence the Saracens, following Eastern nations, gave the designation "the Active Intellect." They believed that the soul of man emanated from it, as a rain-drop comes from the sea, and, after a season, returns.

So arose among them the imposing doctrines of emanation and absorption.