There are many problems in natural science on which we cannot fittingly speak unless we call metaphysics to our aid; but not the wisdom of the schools, which consists in mere verbiage. It is that which was before physics, exists with it, and will be after it.
Since men are really interested in nothing but their own opinions, every one who puts forward an opinion looks about him right and left for means of strengthening himself and others in it. A man avails himself of the truth so long as it is serviceable; but he seizes on what is false with a passionate eloquence as soon as he can make a momentary use of it; whether it be to dazzle others with it as a kind of half-truth, or to employ it as a stopgap for effecting an apparent union between things that have been disjointed. This experience at first caused me annoyance, and then sorrow; and now it is a source of mischievous satisfaction. I have pledged myself never again to expose a proceeding of this kind.
Everything that we call Invention or Discovery in the higher sense of the word is the serious exercise and activity of an original feeling for truth, which, after a long course of silent cultivation, suddenly flashes out into fruitful knowledge. It is a revelation working from within on the outer world, and lets a man feel that he is made in the image of God. It is a synthesis of World and Mind, giving the most blessed assurance of the eternal harmony of things.
A man must cling to the belief that the incomprehensible is comprehensible; otherwise he would not try to fathom it.
There are pedants who are also rascals, and they are the worst of all.