none1noReverse Complexity is a long term research program aiming at discovering the abstract, logical principles underlying Complexity Theory, by means of a formal, reverse analysis of its proofs. The final goal is to get a cleaner, machine independent presentation of the foundation of Complexity Theory and a better, synergic integration with logic; in particular, we aim to provide abstract, axiomatic characterizations of Complexity Classes with the purpose to better grasp their essence, identify their distinctive properties, suggest new, possibly non-standard computational models and finally provide new tools for separating them. In this article, we introduce the program and illustrate its methodology through an investigation of the well k...