Don Juan monologue (Act 3) — Man and Superman

But I should not have them if they served no purpose. And I, my friend, am as much a part of Nature as my own finger is a part of me. If my finger is the organ by which I grasp the sword and the mandoline, my brain is the organ by which Nature strives to understand itself. My dog's brain serves only my dog's purposes; but my brain labors at a knowledge which does nothing for me personally but make my body bitter to me and my decay and death a calamity. Were I not possessed with a purpose beyond my own I had better be a ploughman than a philosopher; for the ploughman lives as long as the philosopher, eats more, sleeps better, and rejoices in the wife of his bosom with less misgiving. This is because the philosopher is in the grip of the Life Force. This Life Force says to him "I have done a thousand wonderful things unconsciously by merely willing to live and following the line of least resistance: now I want to know myself and my destination, and choose my path; so I have made a special brain--a philosopher's brain--to grasp this knowledge for me as the husbandman's hand grasps the plough for me. And this" says the Life Force to the philosopher "must thou strive to do for me until thou diest, when I will make another brain and another philosopher to carry on the work."