Why did Claude Bernard defend vivisection as part of physiological research?

Claude Bernard, a foundational figure in experimental medicine, argued that vivisection was indispensable for physiological research. In his seminal work, An Introduction to the Study of Experimental Medicine, he posited that to advance, medicine must be firmly grounded in experimental physiology.

Bernard maintained that the processes of life are mechanistically determined by physico-chemical forces. Because he believed that biology depends on understanding these deterministic processes, he viewed the direct observation and manipulation of living organisms as a necessary scientific method. By moving beyond the vague concept of a "vital force," he sought to establish a rigorous, evidence-based approach to understanding how the body functions, including his discovery of the internal environment (milieu intérieur).

While the ethics of animal experimentation remain a subject of significant debate—with modern perspectives often emphasizing the necessity of minimizing suffering and utilizing alternatives—Bernard’s defense was rooted in the conviction that such research was the only way to achieve the empirical precision required to transform medicine into a true science.123