 All these objections purport to have characterized a creature with the functional organization of normal human beings, but without any, or the right sort, of qualia (or vice versa), and thus to have produced a counterexample to functional theories of experiential states. One line of response, initially advanced by Sydney Shoemaker (1994b), is that although functional duplicates of ourselves with inverted qualia may be possible, duplicates with absent qualia are not, since their possibility leads to untenable skepticism about the qualitative character of one's own mental states. This argument has been challenged, however (Block 1980b; but see Shoemaker's response in 1994d, and Balog, 1999, for a related view), and the more common response to these objections—particularly to the absent qualia objection— is to question whether scenarios involving creatures such as Blockheads provide genuine counterexamples to functionalist theories of experiential states. 