“We hear and apprehend only what we already half know.”

“A man receives only what he is ready to receive, whether physically or intellectually or morally, as animals conceive at certain seasons their kind only. We hear and apprehend only what we already half know. If there is something which does not concern me, which is out of my line, which by experience or by genius my attention is not drawn to, however novel and remarkable it may be, if it is spoken, we hear it not, if it is written, we read it not, or if we read it, it does not detain us. Every man thus tracks himself through life, in all his hearing and reading and observation and traveling. His observations make a chain. The phenomenon or fact that cannot in any wise be linked with the rest which he has observed, he does not observe. By and by we may be ready to receive what we cannot receive now. I find, for example, in Aristotle some thing about the spawning, etc., of the pout and perch, because I know something about it already and have my attention aroused; but I do not discover till very late that he has made other equally important observations on the spawning of other fishes, because I am not interested in those fishes.”

“Sometimes we are inclined to class those who are once-and-a-half witted with the half-witted, because we appreciate only a third part of their wit.”

“To know that we know what we know, and that we do not know what we do not know, that is true knowledge.”

“Confucius said, "To know that we know what we know, and that we do not know what we do not know, that is true knowledge.”

“In the long run, we only hit what we aim at.”

“I think that we may safely trust a good deal more than we do. We may waive just so much care of ourselves as we honestly bestow elsewhere. Nature is well adapted to our weakness as our strength. The incessant anxiety and strain of some is a well nigh incurable form of disease. We are made to exaggerate the importance of what work we do; and yet how much is not done by us! or, what if we had been taken sick? How vigilant we are! determined not to live by faith if we can avoid it; all the day long on the alert, at night we unwillingly say our prayers and commit ourselves to uncertainties. So thoroughly and sincerely are we compelled to live, reverencing our life, and denying the possibility of change. This is the only way, we say; but there are as many ways as there can be drawn radii from one centre. All change is a miracle to contemplate; but it is a miracle which is taking place every instant. Confucius said, “To know that we know what we know, and that we do not know what we do not know, that is true knowledge.” When one man has reduced a fact of the imagination to be a fact to his understanding, I foresee that all men will at length establish their lives on that basis.”