What was it about, in its forms and contents, "that strange and extraordinary dialogue" that in 1939 Spinelli entertained with Colorni and that continued until the latter’s departure from Ventotene? The answer is unveiled (in part) by these "Socratic" dialogues between Altiero and Eugenio, which are collected here for the first time. Because by following their relationship it is finally possible to have a concrete idea of ​​the evolution of the cultural discussion between these two protagonists of the "Ventotene group", that is of that important page of theoretical elaboration that developed in parallel with the federalist political debate that led to the “Ventotene Manifesto”. It is an intellectual research without boundaries, dealing with key cognitive themes related to numerous disciplines (such as systems, love, philosophy, science, goals and means, anthropomorphism, economics, action, success, detachment) addressed in a very accessible dialogical form, which over and again intellectually challenge the interlocutor (and the reader) in an often entertaining way. It is an iconoclastic, liberating, fantastic feat of learning that develops in almost prohibitive conditions; and from which, without a doubt, we all can learn a lot.