||Theories of rationality should ideally provide us with tools for a number of important tasks: We want to avoid irrationality, or aim at justifying our beliefs and decisions by certain standards. We want to be clear about whether the reasons for our beliefs and actions are valid or reasonable. Furthermore, we often have to communicate with others about our beliefs and decisions, such as in scientific, ethical, economic, or political contexts. All this requires conceptions or even theories of reason or rationality. Such theories are then highly important for episemology, philosophy of science, ethics, political philosophy, and the philosophy of mind and action. But what do we mean when we say that something, or someone, is rational (or irrational)? What are the normative standards of rationality? How should a theory of rationality be built? What are its presuppositions, its potentials and limits? What role does science play in it, and what is scientific rationality itself? In the answers to such questions, different thinkers have introduced a bewildering variety of distinctions - such as theoretical versus practical, instrumental versus non-instrumental, individual versus collective, formal versus 1 Racionalitat 2015 - 2016 content-based, or optimizing versus "bounded" concepts of rationality. The course presents a selection of both classical and current debates in which such understandings of rationality or reason emerge, adressing both the history of the concepts as well as their significance at the intersection between philosophy and the sciences.