Pierre Charles Alexandre Louis (1787–1872) was a French physician, known for introducing the use of the "numerical method" in the field of medicine — i.e., the concept that knowledge about a disease, its history, clinical presentation and treatment, could be derived from aggregated patient data.
Louis became known for his research on tuberculosis and typhoid fever and for the controversy that opposed him to François Joseph Victor Broussais about the use of bloodletting in the treatment of pneumonitis (today pneumonia). It was in 1835 that Louis published Researches sur les effets de la saigneé dans quelques maladies inflammatoires in which he utilized the numerical method to prove that bloodletting was an ineffective treatment for the various fevers. He advocated a méthode expectante in place of bloodletting.