falsifiability

Falsifiability is a concept in the philosophy of science, associated most closely with Karl Popper. A theory is falsifiable if it makes predictions that could, in principle, be tested and shown to be false. The core idea is testability: for a claim to be scientific, it must be structured in a way that could be contradicted by evidence.

As a demarcation criterion, falsifiability is intended to distinguish scientific theories from non-scientific or metaphysical assertions. Science progresses, according to this view, by formulating bold conjectures and subjecting them to rigorous attempts at refutation, rather than by accumulating confirming examples alone.

Historical and contemporary examples illustrate the idea. The phlogiston theory of combustion was undermined by experiments showing mass changes consistent with oxygen uptake, leading to its abandonment. The geocentric model gave way to heliocentrism as observational evidence accumulated. In physics, general relativity makes precise, testable predictions (such as light deflection) that can, in principle, falsify the theory if contradicted by data.

Critics note several limitations. The Duhem-Quine problem shows that testing a theory often involves many auxiliary assumptions, which can be adjusted to preserve a theory in the face of conflicting data. Some domains are difficult to falsify, and some claimed scientific theories resist refutation due to protective belt reasoning or conceptual shifts. Consequently, falsifiability is often complemented by other criteria, such as explanatory power and coherence with established theories.

Despite criticisms, falsifiability remains a influential standard in evaluating scientific status, guiding the formulation of testable predictions and helping distinguish science from non-science and pseudoscience.