The instructor went forward a few pages more in his exhaustive volume. He had attended all the lectures but three throughout the year, taking them down in short-hand. Laryngitis had kept him from those three, to which however, he had sent a stenographic friend so that the chain was unbroken. He now took up the next philosopher on the list; but his smooth discourse was, after a short while, rudely shaken. It was the second tennis boy questioning severely the doctrines imparted. “So he says color is all your eye, and shape isn’t? and substance isn’t?” “Do you mean he claims,” said the first boy, equally resentful, “that if we were all extinguished the world would still be here, only there’d be no difference between blue and pink, for instance?” “The reason is clear,” responded the tutor, blandly. He adjusted his eyeglasses, placed their elastic cord behind his ear, and referred to his notes. “It is human sight that distinguishes between colors. If human sight be eliminated from the universe, nothing remains to make the distinction, and consequently there will be none. Thus also is it with sounds. If the universe contains no ear to hear the sound, the sound has no existence.” “Why?” said both the tennis boys at once. The tutor smiled. “Is it not clear,” said he, “that there can be no sound if it is not heard!” “No,” they both returned, “not in the least clear.” “It’s clear enough what he’s driving at of course,” pursued the first boy. “Until the waves of sound or light or what not hit us through our senses, our brains don’t experience the sensations of sound or light or what not, and so, of course, we can’t know about them--not until they reach us.” “Precisely,” said the tutor. He had a suave and slightly alien accent. “Well, just tell me how that proves a thunder-storm in a desert island makes no noise.” “If a thing is inaudible--” began the tutor. “That’s mere juggling!” vociferated the boy, “That’s merely the same kind of toy-shop brain-trick you gave us out of Greek philosophy yesterday. They said there was no such thing as motion because at every instant of time the moving body had to be somewhere, so how could it get anywhere else? Good Lord! I can make up foolishness like that myself. For instance: A moving body can never stop. Why? Why, because at every instant of time it must be going at a certain rate, so how can it ever get slower? Pooh!” He stopped. He had been gesticulating with one hand, which he now jammed wrathfully into his pocket. The tutor must have derived great pleasure from his own smile, for he prolonged and deepened and variously modified it while his shiny little calculating eyes travelled from one to the other of his ruddy scholars. He coughed, consulted his notes, and went through all the paces of superiority. “I can find nothing about a body’s being unable to stop,” said he, gently. “If logic makes no appeal to you, gentlemen--”