This article presents a relational criticism of the "morphogenetic theory" of M. Archer. This theory is founded and representative of the most influential mode of perception of the social universe of the last few decades: co-determinism (structure ↔ agency). Co-determinism's influence can be explained by its integration of modern general presuppositions like freedom, individualism, and the quest for a new social order. By identifying five basic principles of relational sociology, we see that Archer's co-deterministic theory offers a complicated solution to (...) avoid voluntarism and co-determinism, limits the potential of sociological imagination, cannot adequately see the fluidity of social processes, produces a certain reification of social structures and agency, and is based on an inconsistent use of egocentric and relational perspectives. These problems can be avoided if we use a relational approach (actor ↔ actor ⇒ structures) based on the study of complex and empirical trans-actions. (shrink)