Lakatos (1922–1974) described a scientific method to both allow for progress and explain how science had developed. Instead of talking about theories, he introduced the notion of a “research program,” which consisted of both theories and accepted research practices in a given field. Every research program has a core, or “protective belt,” of claims that could not be falsified.

Degenerating research programs have growing protective belts and fail to predict new facts or create new projects for discovery; they survive by adding ad hoc hypotheses. Progressive research programs are able to support new projects of discovery that do not produce vast amounts of falsifying data requiring revision of the core; they do not significantly rely on ad hoc hypotheses.

The way that Lakatos reconciled the discrepancy between Popper and Kuhn’s account of science was to shift ground from the static relationship between facts and theories to the dynamic nature of scientific practice. Popper’s view was that scientific truth changes when theories are falsified, whereas Kuhn thought that theories were not falsified so much as overthrown. Lakatos made scientific practice, rather than beliefs about the truth of theories, his subject.