“We very often express in a categorical form a judgment of which we do not feel assured, we even lay stress on its absolute validity. We want to see what opposition it will arouse, and this can be achieved only by stating our assumption not as a tentative suggestion, which no one will consider, but as an irrefutable, all-important truth. The greater the value of the assumption has for us, the more carefully do we conceal any suggestion of its improbability.”