Growth means change. If a man grows after thirty years he must necessarily change. Many men probably reach their intellectual height long before they have lived thirty years, and spend the balance of their lives in defending the mistakes of their youth. A great man continues to grow until his death, and growth--as I said before--means change. Darwin was continually finding new facts, and kept his mind as open to a new truth as the East is to the rising of another sun. Humboldt at the age of ninety maintained the attitude of a pupil, and was, until the moment of his death, willing to learn. The more a man knows, the more willing he is to learn. The less a man knows, the more positive, a? is that he knows everything. The smallest minds mature the earliest. The less there is to a man the quicker he attains his growth. I have known many people who reached their intellectual height while in their mother's arms. I have known people who were exceedingly smart babies to become excessively stupid people. It is with men as with other things. The mullein needs only a year, but the oak a century, and the greatest men are those who have continued to grow as long as they have lived. Small people delight in what they call consistency--that is, it gives them immense pleasure to say that they believe now exactly as they did ten years ago. This simply amounts to a certificate that they have not grown--that they have not developed--and that they know just as little now as they ever did. The highest possible conception of consistency is to be true to the knowledge of to-day, without the slightest reference to what your opinion was years ago. There is another view of this subject. Few men have settled opinions before or at thirty. Of course, I do not include persons of genius. At thirty the passions have, as a rule, too much influence; the intellect is not the pilot. At thirty most men have prejudices rather than opinions--that is to say, rather than judgments--and few men have lived to be sixty without materially modifying the opinions they held at thirty. As I said in the first place, much depends on the shape, quality and quantity of brain; much depends on mental and moral courage. There are many people with great physical courage who are afraid to express their opinions; men who will meet death without a tremor and will yet hesitate to express their views. So, much depends on the character of the people among whom we live. A man in the old times living in New England thought several times before he expressed any opinion contrary to the views of the majority. But if the people have intellectual hospitality, then men express their views--and it may be that we change somewhat in proportion to the decency of our neighbors. In the old times it was thought that God was opposed to any change of opinion, and that nothing so excited the auger of the deity as the expression of a new thought. That idea is fading away.