Starting with two quotations from Pascal and Goya, with their polysemy and ambiguities, the article explores the oppositions between reason and feelings, reason and madness, reason and fantasy. It stresses Freud's open rationality, which allows us to account for the paradoxes of emotional life that previously seemed merely irrational. It emphasizes the power of reason, particularly in the scientific method, but also what transcends it, what, without minimizing it, reveals its limits (overlooked by scientists). With the help of a brief clinical example, which evidences potentially delusional thinking but remains anchored in common reality, it distinguishes between an irrationality that attacks scientific methods and results, that is alienating and sometimes destructive, and a nond-efensive irrationality, marked by the infantile and aspirations for the unlimited, which is an opening to creativity and therefore to the expansion and renewal of rationality itself.