That the so-called proofs of propositions like that concerning the equilibrium of the lever, the relation of space and time in gravitation, etc., which applied mathematics frequently gives, should be taken and given as proofs, is itself merely a proof of how great the need is for knowledge to have a process of proof, seeing that, even where proof is not to be had, knowledge yet puts a value on the mere semblance of it, and gets thereby a certain sense of satisfaction.
Honako esakuneen frogapen deitzen zaien horiek, adibidez, burdinagaren orekarena, espazioaren eta denboraren erlazioa erorketaren higiduran, eta abarrena, matematika aplikatuak hainbeste eskaintzen dituen horiek frogapentzat eman eta halakotzat onartzea honen frogapena baino ez da, zein handia den frogatzearen premia ezagutzearentzat, zeren hori ez duenean haren itxura soila ere errespetatzen baitu eta horren bidez asebetetzen baita.