Why did John Stuart Mill believe scientific methods could be applied to social and moral questions?

John Stuart Mill believed that scientific methods could be applied to social and moral questions because he sought to establish an "unimpeachable method of proof" for conclusions in these fields, mirroring the success of the natural sciences.1

Inspired by the physics of Isaac Newton, which served as a model of scientific exposition for earlier thinkers, Mill aimed to formulate a logic of the human sciences—including sociology, psychology, and history—based on causal explanation. In his work A System of Logic, he developed a thoroughly empiricist theory of knowledge, arguing that all real knowledge is inductive and empirical.123

While he was influenced by the French positivist Auguste Comte, who maintained that social sciences should proceed from observations to general laws, Mill sought to integrate this new inductive logic with traditional methods, ensuring his approach supplemented rather than superseded existing logical frameworks. Ultimately, Mill viewed this scientific rigor as essential for deducing principles suitable for any given social or political circumstance.21