So I did it. Brrrrrrrup--I stuck my finger in, and I started to read: "Triboluminescence. Triboluminescence is the light emitted when crystals are crushed..."The previous pages had examples of students who knew all the rules for polarization and refraction, without having it occur to them that light off a bay is polarized, or that glass has an index of refraction. (This would have been in 1951.)
I said, "And there, have you got science? No. You have only told what a word means in terms of other words. You haven't told anything about nature--what crystals produce light when you crush them, why they produce light. Did you see any student go home and try it? He can't.
"But if, instead, you were to write, 'When you take a lump of sugar and crush it with a pair of pliers in the dark, you can see a bluish flash. Some other crystals do that too. Nobody knows why. The phenomenon is called "triboluminescence"'. Then somebody will go home and try it. Then there's an experience of nature.
Elsewhere Feynman speaks of listening to and intervening in talks in Japan:
He thinks I'm following the steps mathematically, but that's not what I'm doing. I have the specific, physical example of what he's trying to analyze, and I know from instinct and experience the properties of the thing. So when the equation says it should be have so-and-so, and I know that's the wrong way around, I jump up and say, "Wait! There's a mistake!"Chapter VII of the Supplements to the First Book, in the second volume of The World as Will and Representation, has the title "On the Relation of Knowledge of Perception to Abstract Knowledge". Schopenhauer writes that
On the other hand, to perceive, to allow the things themselves to speak to us, to apprehend and grasp new relations between them, and then to precipitate and deposit all this into new concepts, in order to possess it with certainty; this is what gives us new knowledge. But whereas almost everyone is capable of comparing concepts with concepts, to compare concepts with perceptions is a gift of the select few. ... Even writing and speaking, whether didactic or poetical, have as their ultimate aim the guidance of the reader to that knowledge of perception from which the author started; if they do not have this aim, they are bad. For this reason the contemplation and observation of everything actual, as soon as it presents something new to the observer, is more instructive than all reading and hearing about it....
With most books, quite apart from the really bad ones, if they are not entirely of empirical content, it is true that the author has thought but not perceived; he has written from reflection, not from intuition. .. I will introduce the difference here touched on by a quite easy and simple example. Every commonplace writer will describe profound contemplation or petrified astonishment by saying: "He stood like a statue"; but Cervantes says: "Like a draped statue; for the wind moved his garments" (Don Quixote, Bk. vi, ch. 19). In such a way have all great minds always thought in the presence of perception, and in their thinking kept their gaze steadily on it. We recognize this, among other things, in the fact that even the most heterogeneous of them so often agree and concur in detail, just because they all speak of the same thing which they all had before their eyes, namely the world, the actuality of perception.