 For example, some theorists (Dennett 1978; Levin 1985; Van Gulick 1989) argue that these scenarios provide clear-cut counterexamples only to crude functional theories, and that attention to the subtleties of more sophisticated characterizations will undermine the intuition that functional duplicates of ourselves with absent qualia are possible (or, conversely, that there are qualitative states without distinctive functional roles). The plausibility of this line of defense is often questioned, however, since there is tension between the goal of increasing the sophistication (and thus the individuative powers) of the functional definitions, and the goal (for analytic functionalists) of keeping these definitions within the bounds of the a priori (though see Section 4.2), or (for psycho-functionalists) broad enough to be instantiable by creatures other than human beings. A related suggestion is that absent qualia seem possible only because of our imaginative shortcomings, in particular, that it is hard for us to attend, at any one time, to all the relevant features of even the simplest functional characterization of experiential states; another is that the intuition that Blockheads lack qualia is based on prejudice—against creatures with unfamiliar shapes and extended reaction times (Dennett 1978), or creatures with parts widely distributed in space (Lycan, 1981, Schwitzgebel 2015 and commentary).