Definition
Philosophy of science is the branch of philosophy that examines the foundations, methods, structure, and implications of science.
It asks what distinguishes scientific knowledge from other forms of belief, how scientific theories are constructed and tested, why some theories replace others, and what — if anything — successful theories tell us about the world as it really is.
Why it matters
How it works
Modern philosophy of science took shape in the early twentieth century with the Vienna Circle's logical positivism, which sought to ground science purely in observation and logical inference. The program ran into trouble: theoretical terms like "electron" cannot be fully reduced to observation, and the principle of induction itself resists logical justification.
Karl Popper's falsificationism offered a different criterion: scientific theories are not those that can be conclusively verified, but those that can in principle be refuted by observation. A statement that cannot be falsified — that no possible evidence could count against — is not scientific. This gave a sharp tool for distinguishing physics from astrology, but it has its own difficulties: theories are typically tested as networks, not in isolation, so any single failure can in principle be blamed on auxiliary assumptions (the Duhem-Quine thesis).
Thomas Kuhn's Structure of Scientific Revolutions (1962) reframed the debate again. Science proceeds, he argued, through long periods of "normal science" within an accepted paradigm, punctuated by revolutionary shifts when anomalies accumulate. Successor theories are not strictly derivable from their predecessors; they involve genuine reconceptualization. Imre Lakatos tried to recover progress without Popper's strict falsificationism by distinguishing "progressive" from "degenerating" research programmes. Newer work on scientific models, idealization, social epistemology of science, and the realism debate continues to refine and complicate the picture.