Wagner’s opera Parsifal is “read” with the help of Bion’s theory of thinking in order to discover psychoanalytic “truths” implicit in it. These are then returned to Bion’s model in order to further elaborate the theory itself. It is suggested the opera contains within it the idea that compassion may be used as an element of psychoanalysis in theory-building, particularly in order to combine it in the psychoanalytic theory of thinking. Bion intuited infantile sexuality as a component of the container/contained function, but did not formulate this in his model. It is suggested that Parsifal offers such a formulation, with compassion as an adjunct to the container/contained gained in the context of infantile sexuality. The rationale for such use of myth and art in psychoanalytic theory is examined, also with the help of Bion’s thinking. This may serve as a demonstration of the use of myth and art in general, and opera in particular, in interdisciplinary exchanges that may enrich both psychoanalysis and the understanding of artworks.