The method of scientific investigation is nothing but the expression of the necessary mode of working of the human mind.

Huxley’s remark frames “the scientific method” not as an artificial set of laboratory rules but as a disciplined extension of ordinary human reasoning. On this view, science succeeds because it systematizes what minds must do to understand the world: observe, compare, infer causes, test expectations against experience, and revise beliefs when evidence resists them. The claim also serves a polemical purpose typical of Huxley’s public writing—defending science as a universal mode of inquiry rather than a narrow professional craft, and implying that resistance to scientific conclusions is often resistance to the mind’s own best habits. It elevates science from technique to epistemology: a norm for responsible thinking.