Cogitations is the name Bion gave to the occasional short notes he had begun to write in the February of 1958 in order to clarify his think-ing about the difficulties of working with psychotic patients using an unmodified psychoanalytic method – work informed by and shared with his two closest colleagues (who, like Bion, were in analysis with Melanie Klein), Hanna Segal and Herbert Rosenfeld. That clinical work formed the foundation of the clinical papers reproduced in Second Thoughts and the formulations in the four books of the 1960s: Learning from Expe-rience, Elements of Psycho-Analysis, Transformations, and Attention and Interpretation.