propensio

Propensio is a term used to denote an intrinsic tendency of a system to produce certain outcomes, particularly in discussions of probability and causation. The word derives from Latin propensio, meaning an inclination or leaning, and appears in historical philosophical writings as a Latinized form of propensity.

In philosophy, propensio is associated with the propensity theory of probability. According to this view, probability expresses a dispositional tendency of a given setup to yield particular outcomes when the experiment is repeated under similar conditions. Proponents treat probabilities as physical propensities of situations, not merely frequencies or degrees of belief. The concept has been linked with the work of philosophers such as Karl Popper, who used propensity as a way to analyze randomness and causation.

In modern practice, the English word propensity is more commonly encountered, for example in the term propensity score used in causal inference to balance covariates in observational studies. The Latin form propensio is less common today, but the underlying idea—an intrinsic tendency that governs outcomes—persists in discussions of model assumptions, causality, and risk assessment.

Limitations and debates: Propensio-like accounts aim to ground probability in dispositional tendencies of systems, but critics argue that propensities can be difficult to verify empirically and may blur the line between physical causation and statistical regularities. Nevertheless, the notion continues to influence debates in philosophy of science, statistics, and related disciplines. See also: propensity score, propensity theory of probability, dispositionalism, causality.