Sincerity: a Study in the Atmosphere of Human Relations, a previously unpublished book, appearing in D. Meltzer's Collected Papers, explores The Dwarfs, The Birthday Party and The Homecoming by Harold Pinter, both the capacity to communicate genuine emotion and its limitation by the subject's inability to say-what-he-means, because of rigidity and coldness, and to mean-what-he-says, because of an integrated narcissistic structure. That the language of dreams is perhaps the lingua franca of emotionality and the key to aesthetics is the book's conclusion, with a clear indication of the books to come. This article surveys the relevance of the notion of sincerity in Meltzer's further work, in its clinical and metapsychological aspects.