Abstract
The aim of this contribution is to clarify the long-standing debate on the transitions between micro and macro levels and to demonstrate that, more than any other paradigm, methodological individualism proposes sound solutions even if it is not always able to offer satisfactory elucidations of certain tricky questions. A tri-dimensional definition of the micro and the macro is put forward. It takes into account the nature of the problem to be solved, the type of hypothesis or simplification the researcher suggests to solve the puzzle, and the nature of the observation unit and the analysis which should be appropriate. While analyzing the manifold transitions between classes of phenomena, the author will bring to light and underscore the unexpected consequences of individual actions or collective decisions. Four cases result from the combination of the micro and the macro: it will be shown that methodological individualism remains the most promising and satisfactory scientific program insofar as it makes possible and defines methodological procedures that allow macro to be based on micro, and to make macro-macro, micro-micro, and macro–micro relationships intelligible. Several well-known historical and theoretical examples are called upon and studied to illustrate the approach and to attest its cognitive power.