Você está se referindo à citação abaixo de Deuses Pequenos entre o Grande Deus Om (atualmente na forma de um pequena tartaruga) e seu acólito Irmão Brutha (atualmente sob a forma de um jovem ligeiramente confuso) sobre o valor relativo dos filósofos para a sociedade.
“The reason why Omnia hasn’t got much of a fleet any more,” said Om. “That’s why it’s always worth having a few philosophers around the place. One minute it’s all Is Truth Beauty and Is Beauty Truth, and Does a Falling Tree in the Forest Make a Sound if There’s No one There to Hear It, and then just when you think they’re going to start dribbling one of ’em says, Incidentally, putting a thirty-foot parabolic reflector on a high place to shoot the rays of the sun at an enemy’s ships would be a very interesting demonstration of optical principles,” he added. “Always coming up with amazing new ideas, the philosophers. The one before that was some intricate device that demonstrated the principles of leverage by incidentally hurling balls of burning sulphur two miles. Then before that, I think, there was some kind of an underwater thing that shot sharpened logs into the bottom of ships.”