How the quarrelsome ‘Jena set’ paved the way for Hitler

Today, the German city of Jena, 150 miles south-west of Berlin, is the world centre of the optical and precision industry; but in the 1790s it spawned an even more marketable commodity. It was then a small medieval town on the banks of the river Saale with crumbling walls, 800 half-timbered houses, a market square and an unruly university. Here, in the philosophy department, Johann Gottlieb Fichte, a young professor inspired by Immanuel Kant and the French Revolution, proclaimed from the pulpit his theory of the ‘Ich’. ‘A person,’ he roared, ‘should be self-determined.’ In an age of absolute power and the divine right of kings, the idea of free will was an incendiary device and Fichte freewheeled his way through each lecture. ‘Attend to yourself,’ he instructed his mesmerised followers; ‘turn your eye away from all that surrounds you and in towards your own inner self.’ Fichte’s lectures, says Andrea Wulf in her engrossing new book, re-centred the way we understand the world.