Often, as in the proposition of Pythagoras, lines are drawn, we don't know why, and it afterwards appears that they were traps which close unexpectedly and take prisoner the assent of the astonished learner, who must now admit what remains wholly inconceivable in its inner connection, so much so, that he may study the whole of Euclid through and through without gaining a real insight into the laws of space-relations, but instead of them he only learns by heart certain results which follow from them.
Sarritan, Pitagorasen teoreman bezala, lerroak marratzen dira, zergatik jakin gabe: gero agertzen da lakioak zirela, ikaslea ustekabean erakarri eta assensus-a atzemateko, zeinek gero harriturik onartu egin behar baitu, bere barne-loturaren arabera erabat ulertezina zaiona, hainbesteraino, non Euklides osoa alderen alde azter baitezake harreman espazialen legeak propioki ulertzea lortu gabe, horren ordez haietatik emaitza batzuk buruz ikasiz.