(concludes the book of the mind with a study of how to preserve and develop its powers for the protection of our lives and the lives of all men.)

someone wrote me the other day, asking, "when is the best time to acquire knowledge?" i answer, "the time is now." it is easier to learn things when you are young, but you cannot be young when you want to be, and if you are old, the best time to acquire knowledge is when you are old. it is true that the brain-cells seem to harden like the body, and it is less easy for them to take on new impressions; but it can be done, and just as seneca began to learn greek at eighty, i know several old men whom the recent war has shaken out of their grooves of thought and compelled to deal with modern ideas.

but if you are young, then so much the better! then the divine thrill of curiosity is keenest; then your memory is fresh, and can be trained; your mind is plastic, and you can form sound habits. you can teach yourself to respect truth and to seek it, you can teach yourself accuracy, open-mindedness, flexibility, persistence in the search for understanding.

first of all, i think, is accuracy. learn to think straight! let your mind be as a sharp scalpel, penetrating unrealities and falsehoods, cutting its way to the facts. when you set out to deal with a certain subject, acquire mastery of it, so that you can say, "i know." and yet, never be too sure that you know! never be so sure, that you are not willing to consider new facts, and to change your way of thinking if it should be necessary. i look about me at the world, and see tigers and serpents, dynamite and poison gas and forty-two centimeter shells—yet i see nothing in the world so deadly to men as an error of the mind. look at the mental follies about you! look at the prejudices, the delusions, the lies deliberately maintained—and realize the waste of it all, the pity of it all!

every man, it seems, has his pet delusions, which he hugs to his bosom and loves because they are his own. if you try to deprive him of those delusions, it is as though you tore from a woman's arms the child she has borne. i have written a book called "the profits of religion," and never a week passes that there do not come to me letters from people who tell me they have read this book with pleasure and profit, they are grateful to me for teaching them so much about the follies and delusions of mankind, and it is all right and all true, save for two or three pages, in which i deal with the special hobby which happens to be their hobby! what i say about all the other creeds is correct—but i fail to understand that the mormon religion is a dignified and inspired religion, a gift from on high, and if only i would carefully study the "book of mormon," i would realize my error! or it is all right, except what i say about the christian scientists, or the theosophists, or perhaps one particular sect of the theosophists, who are different from the others. today there lies upon my desk a letter from a man who has read many of my books, and now is grief-stricken because he must part company from me; he discovers that i permit myself to speak disrespectfully about the seventh day adventist religion, whereas he is prepared to show the marvels of biblical prophecy now achieving themselves in the world. how could any save a divinely revealed religion have foreseen the present movement to establish the sabbath by law? yes, and presently i shall see the last atom of the prophecy fulfilled—there will be a death penalty for failure to obey the sabbath law!

cultivate the great and precious virtue of open-mindedness. keep your thinking free, not merely from outer compulsions, but from the more deadly compulsions of its own making—from prejudices and superstitions. the prejudices and superstitions of mankind are like those diseased mental states which are discovered by the psychoanalyst; what he calls a "complex" in the subconscious mind, a tangle or knot which is a center of disturbance, and keeps the whole being in a state of confusion. each group of men, each sect or class, have their precious dogmas, their shibboleths, their sacred words and stock phrases which set their whole beings aflame with fanaticism. they have also their phobias, their words of terror, which cannot be spoken in their presence without causing a brain-storm.

at present the dread word of our time is "communist."

you can scarcely say the word without someone telephoning for the police. and yet, when you meet a communist, what is he? a worn and fragile student, who has thought out a way to make the world a better place to live in, and whose crime is that he tells others about his idea! or perhaps you belong to the other side, and then your word of terror is the word "capitalist." you meet a capitalist, and what do you find? very likely you find a man who is kindly, generous in his personal impulses, but bewildered, possibly a little frightened, still more irritated and made stubborn. so you realize that nearly all men are better than the institutions and systems under which they live; you realize the urgent need of applying your reasoning powers to the problem of social reorganization.

cultivate also, in the affairs of your mind, the ancient virtue of humility. there is an oldtime poem, which perhaps was in your school readers, "oh, why should the spirit of mortal be proud?" my answer is, for innumerable reasons. the spirit of mortal should be proud and must be proud because life throbs in it, and because life is a marvelous thing, and the excitement of life is perpetual. yesterday i met a young mother; and of what avail is all the pessimism of poets against the pride of a young mother? "oh!" she cried, and her face lighted up with delight. "he said 'goo'!" yes, he said "goo!"—and never since the world began had there been a baby which had achieved that marvel. presently it will be, "look, look, he is trying to walk!" then he will be getting marks at school, and presently he will be displaying signs of genius. always it will take an effort of the mind of that young mother to realize that there are other children in the world as wonderful as her own; and perhaps it will take many generations of mental effort before there will be young mothers capable of realizing that some other child is more wonderful than her child.

in other words, it is by a definite process of broadening our minds that we come to realize the lives of others, to transfer to them the interest we naturally take in our own lives, and to admit them to a state of equality with ourselves. this is one of the services the mind must render for us; it is the process of civilizing us. and there is another, and yet more important task, which is to make clear to us the fact that we do not altogether make this life of ours, that there is a universe of power and wisdom which is not ours, but on which we draw. "the fear of the lord is the beginning of wisdom," said the psalmist. we know now that fear is an ugly emotion, destructive to life; but it may be purified and made into a true humility, which every thinking man must feel towards life and its miracles.

also the man will have joy, because it is given him to share the high, marvelous adventure of being. to the pleasures of the body there is a limit, and it comes quickly; but the pleasures of the mind are infinite, and no one who truly understands them can have a moment of boredom in life. to a man who possesses the key to modern thought, who knows what knowledge is and where to look for it, the life of the mind is a panorama of delight perpetually unrolled before him. to the minds of our ancestors there was one universe; but to our minds there are many universes, and new ones continually discovered.

the only question is, which one will you choose? will you choose the universe of outer space, the material world of infinity? consider the smallest insect that you can see, crawling upon the surface of the earth; small as that insect is in relation to the earth, it is not so small, by millions of times, as is the earth in relation to the universe made visible to our eyes by the high-power telescope, plus the photographic camera, plus the microscope. if you want to know the miracles of this world of space, read arrhenius' "the life of the universe," or simon newcomb's "sidelights on astronomy." suffice it here to say that we have a chemistry of the stars, by means of the spectroscope; that we can measure the speed and direction of stars by the same means; that we have learned to measure the size of the stars, and are studying stars which we cannot even see! and then along comes einstein, with his theories of "relativity," and makes it seem that we have to revise a great part of this knowledge to allow for the fact that not merely everything we look at, but also we ourselves, are flying every which way through space!

or will you choose the universe of the atom, the infinity of the material world followed the other way, so to speak? big as is the universe in relation to our world, and big as is our world in relation to the insect that crawls on it, the insect is bigger yet in relation to the molecules which compose its body; and these in turn are millions of millions of times bigger than the atoms which compose them; and then, behold, in the atom there are millions of millions of electrons—tiny particles of electric energy! we cannot see these infinitely minute things, any more than we can see the electricity which runs our trolley cars; but we can see their effects, and we can count and measure them, and deal with them in complicated mathematical formulas, and be just as certain of their existence as we are of the dust under our feet. if you wish to explore this wonderland, read duncan's "the new knowledge," or dr. henry smith williams' "miracles of science."

or will you choose the universe of the subconscious, our racial past locked up in the secret chambers of our mind? or will you choose the universe of the superconscious, the infinity of genius manifested in the arts? by the device of art man not merely creates new life, he tests it, he weighs it and measures it, he tries experiments with it, as the physicist with the molecule and the astronomer with light. he finds out what works, and what does not work, and so develops his moral and spiritual muscles, training himself for his task as maker of life.

written words can give but a feeble idea of the wonders that are found in these enchanted regions of the mind. here are palaces of splendor beyond imagining, here are temples with sacred shrines, and treasure-chambers full of gold and priceless jewels. into these places we enter as aladdin in the ancient tale; we are the masters here, and all that we see is ours. he who has once got access to it—he possesses not merely the magic lamp, he possesses all the wonderful fairy properties of all the tales of our childhood. his is the tarnhelm and the magic ring which gives him power over his foes; his is the sword excalibur which none can break, and the silver bullet which brings down all game, and the flying carpet upon which to travel over the earth, and the house made of ginger-bread, and the three wishes which always come true, and the philter of love, and the elixir of youth, and the music of the spheres, and—who knows, some day he may come upon heaven, with st. peter and his golden key, and the seraphim singing, and the happy blest conversing!