Albert Aftalion's exploration into the theory of periodic, general economic crises in an industrial economy outlines a conceptual framework based upon the distinction between the structural conditions that make a crisis possible and the historical triggers that give any particular crisis its specific character. This distinction is key to Aftalion's theory and policy of the medium term and makes his contribution a forerunner of the principle of contextual emergence in complex dynamics. This approach allows Aftalion to distinguish between different, but hierarchically related, causal layers: (i) the fundamental relationship between production and needs: capital formation is a necessary condition in order to achieve an equilibrium between production and needs compatible with increasing (or non-diminishing) per capita welfare; (ii) the more historically specific causal layer at which the lengthening of production processes as a result of the increasing utilization of fixed capital items becomes a central feature and makes it necessary to allow for adjustment periods during which the economic system is out of equilibrium and lack of time co-ordination between production and needs may generate crises; (iii) the most specific level of causation at which different institutional arrangements (e.g., private- versus social-ownership economy) determine the response patterns of individuals and groups to the mismatches characterizing out-of-equilibrium situations. Aftalion's approach highlights causal pluralism in economic dynamics while emphasizing that the different causal triggers are systematically related to one another in a hierarchical way. This intertwining of causal layers is especially relevant in the medium term, which makes the context of medium-term policy decisions the most difficult to detect and, at the same time, of critical importance to the success of policy measures.