Why did Claude Bernard believe scientific experiments need a guiding hypothesis?

Claude Bernard, a foundational figure in experimental medicine, moved beyond the purely empirical methods of his predecessors, such as François Magendie, who conducted experiments without preconceived notions.1

Bernard argued that scientific progress requires a guiding hypothesis because it provides a necessary framework for the experimenter. According to his philosophy, as detailed in his seminal work An Introduction to the Study of Experimental Medicine, the role of the hypothesis is to be either confirmed or refuted by the experimental results. By establishing a clear expectation, the scientist can systematically test the mechanistic, physico-chemical forces that determine biological processes, rather than relying on vague concepts like vital force. This structured approach transformed physiology into a rigorous science, allowing for the discovery of complex biological principles such as homeostasis.12