A cure for schizophrenia, one of the most severe mental diseases, must await an understanding of its origins and pathogenesis, and the search for the origins of schizophrenia has been slowed by several difficulties; not the least of which has been that definition of the disorder has relied exclusively on description of symptoms and the observed course of the disorder. We lack a valid identifying criterion for schizophrenia that would signal its presence. Kraepelin and Bleuler had no such criterion to offer, and therefore they relied on careful description of symptoms. This has resulted in continuing ambiguities and disputes, such as whether or not schizophrenia and manic-depressive illness are distinct syndromes or diseases. Although it is clear that neither disorder is homogeneous, it is not clear that they are distinct from each other, at least from the vantage point of symptoms alone. Resolution of these uncertainties will depend on finding valid markers for a given disorder, that is, indicators of the presence of the disease that may be behavioral, anatomical, or biochemical and are not necessarily coincident or identical with the current defining symptoms of the disease. These markers should help us to advance beyond our current inadequate understanding of the causes of the schizophrenias, to use a term that recognizes the heterogeneity of the condition. I shall describe to you one such marker – a disorder of smooth pursuit eye movements – that has more than mere promise of being such an aid in untangling the mysteries of schizophrenia. This eye movement dysfunction can serve to guide us through the labyrinth of schizophrenic disorganization as Ariadne's thread guided Theseus on his mission to slay the Minotaur.