Thus, in this matter, Einstein takes the same stand as Schopenhauer in the preface of his chief work, in which he says: "To understand this work no better way can be advised than to read it twice (at least), inasmuch as the beginning assumes the end, almost as much as the end assumes the beginning; the smallest part cannot be understood if the whole has not already been understood." Whoever accepts and follows this advice will find that the intermediate objections will gradually balance and cancel one another, and that it is not necessary that they should interrupt the steady and consistent line of development. The position would be different if a disciple of the new theory should resolve to dispense with strictly scientific reasoning altogether, and should wish to meet the wishes of his readers or hearers by discarding accuracy entirely. Such a programme seems quite feasible. "This would be merely following the sketchy method of a magazine," Einstein remarked, "but you do not seriously think that it would lead to anything?" "It would not be a true explanation, which is reserved for technical productions. But I can imagine that it would not be unprofitable to help one who is entirely ignorant on these questions by using makeshifts, in the form of allegories or analogies, which will serve as supports if he should take fright during the course of his earlier studies. These shocks are bound to occur, as, for instance, when he learns that a moving rigid rod undergoes contraction in the direction of motion." "But this is _proved_ to him!" "Nevertheless, he does not easily accept it. For the general reader will say to himself: 'A superhuman effort is imposed on my mind. A rigid rod is the most constant of all things, and never before has one been compelled to regard something that is constant as variable.'" "If he does not grasp it, no analogy will teach him." "But perhaps it is possible. The analogy is to show him that the effort is not _superhuman_, and that thinking Man has already had occasion to become familiar with such transformations from constant to variable factors." "I am afraid your analogy will prove a failure." "From the scientific point of view this is probably true, inasmuch as all comparisons are imperfect, but the analogy may yet be of service as a last resort. For example, I should say to my general reader: 'Picture to yourself a savant of the Middle Ages who reflects on the constitution of animals and plants. One fact seems to him to be irrevocably true, namely, that the species are unchangeable! A palm tree is a palm tree, a horse is a horse, a worm a worm, and what is once a reptile remains a reptile. A species in itself denotes something absolutely _invariant_.'" "The expression is wrong when taken in this connexion; you mean _invariable_."