Thus, for example, a practised billiard-player may have a perfect knowledge of the laws of the impact of elastic bodies upon each other, merely in the understanding, merely for direct perception; and for him it is quite sufficient;
Horrela, adibidez, billar-jokalari trebe batek gorputz elastikoen arteko talka-legeen ezagutza perfektua izan dezake, adimenean soilik, begiespen bitartegaberako, eta horrekin aski du: