This essay will examine the role of Cesare Lombroso's scientific and occult researches in shaping Yeats's view of the mind, whether creative or criminal, in the mystical system of A Vision. A previous generation of critics has not known how to place Yeats's love of detective fiction, much as an earlier generation failed to take serious account of his occult interests. Although the philosophical and aesthetic importance of Yeats's mystical work has recently received serious attention, notably in W. B. Yeats's A Vision: Explications and Contexts (2012), the models used to recuperate and reassess this aspect of Yeats's interest have not so far included minor contemporary figures like Lombroso, but have rather focused on Classical Philosophy, idealism, or political philosophy. Additionally, key work about Yeats and eugenics, from Elizabeth Cullingford (1981) through David Bradshaw (1992) and Marjorie Howes (1998) to Donald Childs (2001), has thus far also omitted to discuss either Lombroso or A Vision in relation to Yeats's eugenics. However, Kathleen Raine reminds us that Yeats had a copy of Lombroso's After Death—What? (1909) in his personal library, though she only uses this as a source of spirit photography rather than considering Yeats's engagement with it. Although Lombroso's work is now largely discredited, he must initially have appeared to Yeats in the role of a Giraldus, in his mixing of scientific and occult knowledge: in a recent essay considering Lombroso's cultural impact and reassessing his occultism, P. J. Ystehede writes that “After Lombroso, ghosts were now also to be found in criminal science.” Moreover, Lombroso's view of different human types, expressed most powerfully in his studies of the criminal and the genius, Criminal Man (1876) and The Man of Genius (1891), could have influenced Yeats's portrayal of representative psychological types as part of the phases of the Great Wheel. Beyond A Vision, Yeats would particularly bring together Lombroso's multiple interests in crime, genius, eugenics, psychoanalysis, predestination, and the occult in his theater: for example, in his late play Purgatory, which will be discussed in detail in its original context of On the Boiler. My aim in this essay is not to offer a comprehensive theory of Yeats and eugenics, as a recent generation of Yeats critics has done, but rather a more specific influence study which looks for a dialogue between Yeats and Lombroso.