Recent literature in philosophy of science has emphasized the idea that some principles play a foundational, constitutive role within the scientific framework in which they operate, providing its conditions of possibility. Following Reichenbach's original interpretation, constitutive principles are regarded as contingent, cognitive principles that must be assumed as preconditions of empirical statements, allowing for the coordination of formal structures with their empirical correlates. This idea of constitutive principles and the connected notion of "coordination" has ramified in interesting ways into different areas of the philosophy of science, especially, but not only, in discussions related to measurement and representation (e.g., van Fraassen 2008). This session explores the idea of constitutive principles in general, starting from its origins, and also by bridging discussions on cognitive constitution with recent developments in the mechanistic literature on phenomena reconstitution. David J. Stump, University of San Francisco - What are Constitutive Principles and What Should They Be? Michele Luchetti, MPIWG and Flavia Padovani, Drexel University - Constituting Phenomena: Cognitive vs Mechanistic Constitution?