I remember some years before, when I was quite young, perhaps no more than fifteen years of age, listening with bated breath to some professors at Leipzig who were talking very excitedly about philosophy in my presence. I had no idea what was meant by philosophy, still less could I follow when they began to discuss Kant’s _Kritik der reinen Vernunft_. One of my friends, whom I looked up to as a great authority, confessed that he had read the book again and again, but could not understand the whole of it. My curiosity was much excited, and once, while he was taking a walk with me, I asked him very timidly what Kant’s book was about, and how a man could write a book that other men could not understand. He tried to explain what Kant’s book was about, but it was all perfect darkness before my eyes; I was trying to lay hold of a word here and there, but it all floated before my mind like mist, without a single ray of light, without any way out of all that maze of words. But when at last he said he would lend me the book, I fell on it and pored over it hour after hour. The result was the same. My little brain could not take in the simplest ideas of the first chapters—that space and time were nothing by themselves; that we ourselves gave the form of space and time to what was given us by the senses. But though defeated I would not give in; I tried again and again, but of course it was all in vain. The words were here and I could construe them, but there was nothing in my mind which the words could have laid hold on. It was like rain on hard soil, it all ran off, or remained standing in puddles and muddles on my poor brain.