Though using Darwin and Freud as examples (not exactly my favorite thinkers), Erikson here does a good job describing creative and intellectual restlessness.
As was indicated in the preface, Freud and Darwin are among the great men who came upon their most decisive contribution only after a change of direction and not without neurotic involvement at the time of the breakthrough to their specific creativity.
Darwin failed in medicine, and had, as if accidentally, embarked on a trip which, in fact, he almost missed because of what seem to have been psychosomatic symptoms. Once aboard the Beagle, however, he found not only boundless physical vigor, but also a keen eye for unexplored details in nature, and a creative discernment leading straight to revolutionary insights: the law of natural selection began to haunt him. He was twenty-seven years old when he came home; he soon became an undiagnosed and lifelong invalid, able only after years of concentrated study to organize his data into a pattern which convincingly supported his ideas.
Freud, too, was already thirty when, as if driven to do so by mere circumstance, he became a practicing neurologist and made psychiatry his laboratory. He had received his medical degree belatedly, having decided to become a medical scientist rather than a doctor at the age of seventeen. His moratorium, which gave him a basic schooling in method while it delayed the development of his specific gift and his revolutionary creativity, was spent in (then physicalistic) physiology. And when he at last did embark on his stupendous lifework, he was almost delayed further by neurotic suffering.
However, a creative man has no choice. He may come across his supreme task almost accidentally. But once the issue is joined, his task proves to be at the same time intimately related to his most personal conflicts, to his superior selective perception, and to the stubbornness of his one-way will: he must court sickness, failure, or insanity, in order to test the alter- native whether the established world will crush him, or whether he will disestablish a sector of this world’s outworn fundaments and make a place for a new one.
-Erik Erikson, Young Man Luther, p.46