Theory

A theory is a well-substantiated explanation of some aspect of the natural world that can incorporate laws, hypotheses, and empirical facts, and that makes testable predictions. In science, a theory represents a high level of generalization that connects and explains a wide range of observations.

Theories are distinguished from hypotheses, which are tentative explanations that require testing, and from laws, which describe consistent regularities or relationships. A theory provides models that explain why phenomena occur and how they relate to one another, organizing evidence into a coherent framework.

The development of a theory involves observation, experimentation, and reasoning, followed by critical evaluation and peer review. Theories are robust but not immutable: they can be revised, refined, or replaced in light of new evidence. They gain predictive power and coherence as more data accumulate, and they may be extended to new domains or contexts.

Notable scientific theories include the theory of evolution by natural selection, germ theory of disease, and the general theory of relativity. Theories also operate in social sciences, informing explanations of behavior, institutions, and social processes. In mathematics, a theory refers to a coherent set of axioms and proven theorems within a formal system, which is logically derived rather than empirically tested.

A theory’s status rests on the weight of evidence and its explanatory breadth, not on absolute proof. The strength of a theory lies in its ability to generate accurate predictions, guide new research, and withstand critical scrutiny over time.