Nicole Oury interviews Hélène Trivouss-Widlöcher on Daniel Widlöcher's role in the creation of the French psychoanalytic Association (APF), and his various commitments as head of a psychiatric department, as President of the APF twice, President of the European Psychoanalytic Federation (EPF), Secretary, and then President of the International Psychoanalytic Association (IPA). He was also a translator of Anna Freud, wrote many books, specified his concept of co-thinking, and always favoured interdisciplinary exchanges. This text tells the story of this tireless advocate.