No More Learning

Then only, when
reason of itself determines the will (not as the servant of the
inclination), it is really a higher desire to which that which is
pathologically           is subordinate, and is really, and even
specifically, distinct from the latter, so that even the slightest
admixture of the motives of the latter impairs its strength and
superiority; just as in a mathematical demonstration the least
empirical condition would degrade and destroy its force and value.