So, again, if a man tries to set forth in writing his views about some difficult problem--social, political, metaphysical, or whatever it may be--the very effort that he makes to express himself clearly and coherently will tend to bring order into the chaos and light into the darkness of his mind, to widen his outlook on his subject, to deepen his insight into it, to bring new aspects of it within the reach of his conscious thought.

And here, as in the case of the child who tries to draw what he sees, there is a continuous reciprocal action between perception and expression, in virtue of which each in turn helps forward the evolution of the other.

Even in so abstract and impersonal a subject as mathematics, the reaction of expression on perception is strong and salutary.

The student who wishes to master a difficult piece of bookwork should try to write it out in his own words; in the effort to set it out concisely and lucidly he will gradually perfect his apprehension of it.

Were he to solve a difficult problem, he would probably regard his grasp of the solution as insecure and incomplete until he had succeeded in making it intelligible to the mind of another.