The Logic of Scientific Discovery in the context of Testability

Falsifiability is a standard of evaluation of scientific theories and hypotheses. A hypothesis is falsifiable if it belongs to a language or logical structure capable of describing an empirical observation that contradicts it. It was introduced by the philosopher of science Karl Popper in his book The Logic of Scientific Discovery (1934). Popper emphasized that the contradiction is to be found in the logical structure alone, without having to worry about methodological considerations external to this structure. He proposed falsifiability as the cornerstone solution to both the problem of induction and the problem of demarcation.

Popper also emphasized the related asymmetry created by the relation of a universal law with basic observation statements and contrasted falsifiability with the intuitively similar concept of verifiability that was then current in the philosophical discipline of logical positivism. He argued that the only way to verify a claim such as "All swans are white" would be if one could empirically observe all swans, which is not possible. On the other hand, the observation of a single black swan is enough to refute this claim.

Testability is a primary aspect of science and the scientific method. There are two components to testability:

1. Falsifiability or defeasibility, which means that counterexamples to the hypothesis are logically possible.
2. The practical feasibility of observing a reproducible series of such counterexamples if they do exist.

In short, a hypothesis is testable if there is a possibility of deciding whether it is true or false based on experimentation by anyone. This allows anyone to decide whether a theory can be supported or refuted by data. However, the interpretation of experimental data may be also inconclusive or uncertain. Karl Popper introduced the concept that scientific knowledge had the property of falsifiability as published in The Logic of Scientific Discovery.

A research program (British English: research programme) is a professional network of scientists conducting basic research. The term was used by philosopher of science Imre Lakatos to blend and revise the normative model of science offered by Karl Popper's The Logic of Scientific Discovery (with its idea of falsifiability) and the descriptive model of science offered by Thomas Kuhn's The Structure of Scientific Revolutions (with its ideas of normal science and paradigm shifts). Lakatos found falsificationism impractical and often not practiced, and found normal science—where a paradigm of science, mimicking an exemplar, extinguishes differing perspectives—more monopolistic than actual.

Lakatos found that many research programs coexisted. Each had a hard core of theories immune to revision, surrounded by a protective belt of malleable theories. A research programme vies against others to be most progressive. Extending the research program's theories into new domains is theoretical progress, and experimentally corroborating such is empirical progress, always refusing falsification of the research program's hard core. A research program might degenerate—lose progressiveness—but later return to progressiveness.