The same may be said of all the great representatives of philosophic thought beginning with Plato and Aristotle, and ending with Hegel, Schopenhauer and Nietzsche. Their works astonish by their power, depth, boldness, beauty and originality of thought. While you read them it seems that truth herself speaks with their lips. And what strong measures of precaution did they take to prevent themselves from being mistaken! They believed in nothing that men had grown accustomed to believe. They methodically doubted everything, reexamined everything, tens, hundreds of times. They gave their life to the truth not in words, but in deed. And still the sum-total is the same in their case as in Kant's: not one of them succeeded in inventing a system free from internal contradictions. Aristotle was already criticising Plato, and the sceptics criticised both of them, and so on until in our day each new thinker struggles with his predecessors, refutes their contradictions and errors, although he knows that he is doomed to the same fate. The historians of philosophy are at infinite pains to conceal the most glaring and noticeable trait of philosophic creation, which is, at bottom, no secret to any one. The uninitiated, and people generally who do not like thinking, and therefore wish to be contemptuous of philosophy, point to the lack of unity among philosophers as evidence that it is not worth while to study philosophy. But they are both wrong. The history of philosophy not only does not inspire us with the thought of the continual evolution of an idea, but palpably convinces us of the contrary, that among philosophers there is not, has not been, and will never be, any aspiration towards unity. Neither will they find in future a truth free from contradiction, for they do not seek the truth in the sense in which the word is understood by the people and by science; and, after all, contradictions do not frighten them, but rather attract. Schopenhauer begins his criticism of Kant's philosophy with the words of Voltaire: 'It is the privilege of genius to make great mistakes with impunity.' I believe that the secret of the philosophic genius lies here. He makes great, the greatest, mistakes, and with impunity. Moreover his mistakes are put to his credit, for the important matter is not his truths, or his judgments, but himself. When you hear from Plato that the life we see is only a shadow, when Spinoza, intoxicated by God, exalts the idea of necessity, when Kant declares that reason dictates laws to Nature,--listening to them you do not examine whether their assertions are true or not, you agree with each of them, whatever he says, and only this question arises in your soul: 'Who is he that speaketh as one having authority?'