 Ryle is often given credit for having shown some of the many difficulties in substance or Cartesian dualism. But the arguments in The Concept of Mind warn of difficulties for any account that takes mental conduct terms to discharge their explanatory role by signifying inner processes: whether irreducibly mental or at bottom physical. Ryle’s target was not merely the ghostliness of the mental processes hypothesized by the Cartesian; it was their essential hidden-ness. The thrust of Ryle’s polemic is that theories about the nature of the alleged referents of the mental concepts we employ in our ordinary everyday commonsense practices cannot make a mystery of this employment without threatening to rob the theories of their subject matter. Our practice of employing such mental concepts would be a complete mystery on a view that takes the “truth-makers” of our mental statements to be not only items within an occult (to others) stream of consciousness, but also on a view that takes them to be items within an occult (to most of us) series of computations or neurological events. Both picture the truth-makers of our claims about other minds or our ascriptions of mental predicates as hidden and thus in practice (if not in principle) as inaccessible.