Helmholtz graduated from the Medical Institute in Berlin in 1843, and subsequently held appointments at Königsberg, Bonn, Heidelberg and Berlin. His physicalist leanings led him to disparage ‘vital forces’, then common in medicine, and to formulate the principle of conservation of energy. Work on hydrodynamics led to fundamental discoveries in topology, and he also studied the physiology of auditory perception. In physics, after an initial defence of the a priori status of Euclidean geometry, Helmholtz repudiated his Kantian heritage and followed the lead of Riemann and Lobachevsky. Helmholtz was the most influential German scientist of the Victorian period, and a leading figure in the conception of science as the search for fundamental laws.