However we select from nature a complex [of phenomena] using the criterion of simplicity, in no case will its theoretical treatment turn out to be forever appropriate (sufficient).... I do not doubt that the day will come when [general relativity], too, will have to yield to another one, for reasons which at present we do not yet surmise. I believe that this process of deepening theory has no limits.
A young man before he leaves the shelter of his father's house, and the guard of a tutor, should be fortify'd with resolution, and made acquainted with men, to secure his virtues, lest he should be led into some ruinous course, or fatal precipice, before he is sufficiently acquainted with the dangers of conversation, and his steadiness enough not to yield to every temptation.
Life continues, and some mornings, weary of the noise, discouraged by the prospect of the interminable work to keep after, sickened also by the madness of the world that leaps at you from the newspaper, finally convinced that i will not be equal to it and that i will disappoint everyone - all i want to do is sit down and wait for evening. This is what i feel like, and sometimes i yield to it.
I have really got it into my head to try to be united states senator, and, if i could have your support, my chances would be reasonably good. But i know, and acknowledge, that you have as just claims to the place as i have; and therefore i cannot ask you to yield to me, if you are thinking of becoming a candidate, yourself. If, however, you are not, then i should like to be remembered affectionately by you; and also to have you make a mark for me with the anti-nebraska members down your way.
But the most brilliant propagandist technique will yield no success unless one fundamental principle is borne in mind constantly and with unflagging attention. It must confine itself to a few points and repeat them over and over. Here, as so often in this world, persistence is the first and most important requirement for success.
The earth is a machine which yields almost gratuitous service to every application of intellect. Every plant is a manufacturer of soil. In the stomach of the plant development begins. The tree can draw on the whole air, the whole earth, on all the rolling main. The plant is all suction-pipe,--imbibing from the ground by its root, from the air by its leaves, with all its might.