Stability theory was inaugurated with Morley's proof of Los' conjecture and its early (though by no means primitive) development was propelled by issues in classification theory.

Many of the essential ideas and results of stability theory, such as Morley rank, Morley sequences, totally transcendental theories, the order property, et cetera, appear already in Morley's proof.

Morley rank was consciously modeled on the transcendence degree in algebraically closed fields. Not only is the theory of algebraically closed fields uncountably categorical, but the nearly century-old proof of this result generalizes almost immediately to other strongly minimal theories and underlies the Baldwin-Lachlan refinement of Morley's categoricity theorem for countable theories.

Explicit appeals to geometry, at the level of incidence geometries, appear in Lachlan's study of totally categorical theories. With Zilber's work on totally categorical theories, sophisticated geometrical algebra plays a central rôle. An important theorem in this habilitation thesis on totally categorical theories already bears the shape of his trichotomy conjecture.