In 1943-44, the British Psycho-Analytical Society held the 'Controversial Discussions' in an attempt to resolve various disagreements then current in the theory, practice and teaching of psychoanalysis. This paper selects and assesses in some detail some of the arguments that emerged around the concepts of 'unconscious phantasy' and 'unconscious conflict'. Inter alia, they included arguments about assumed early events, about ways of interpreting and assessing evidence, about modes and different levels of conceptualisation, about interpretations of Freud and about changes in psychoanalytic theory. Attempts to achieve mutual understanding existed side by side with total and sometimes rancorous disagreement. Attention is given to sometimes irresolvable communicative and conceptual difficulties that arose and still arise, from differences in meaning that different psychoanalytic thinkers assigned and still assign to each of the two conceptual terms, 'unconscious phantasy' and 'unconscious conflict'.