Conventionalism

Conventionalism is the view that certain fundamental principles—in science, logic, ethics or law—are not derived from external reality or from infallible intuition, but rest on explicit or implicit agreements adopted by a community or by an inquirer, and are justified by their usefulness or internal coherence.

The term has its roots in reflection on language. Already in antiquity, the question of whether words mean something by nature or by convention appears in Plato's Cratylus, and some Greek grammarians suggested that languages may have arisen from an agreement among people. In modern linguistics, Ferdinand de Saussure defended the arbitrariness of the sign: there is no necessary link between a word and what it designates. This stands opposed to naturalism, which holds that such a link exists.

In the philosophy of science and mathematics, conventionalism gained prominence with Henri Poincaré, who held that the axioms of geometry are neither a priori truths nor empirical facts, but choices guided by the results they yield rather than by their apparent intuitive obviousness. Pierre Duhem extended this view to all of science, stressing the predictive value of laws over any supposed correspondence with an inaccessible metaphysical reality. Later, logical positivists such as A. J. Ayer and Carl Hempel applied the idea to logic and mathematics, arguing that their truths lack factual content and are useful by convention.

As a simple example, the choice of a system of measurement or of coordinates reflects practical agreements; changing it does not alter the facts, though it changes how they are described.

Conventionalism remains debated. Critics argue that not everything can be reduced to agreement, and that some truths seem to impose themselves regardless of our decisions. In moral and legal theory, the question is whether norms rest solely on social conventions or also on deeper principles.