 Some have argued that Mary would recognize the colors when first seeing them on the basis of her complete physical knowledge about color vision (see Hardin 1992). According to this claim she would think something like “oh, so this is red” when first confronted with a red patch and she could not be fooled by what Dennett calls ‘the blue banana trick’: when shown a blue banana she would know that it has the wrong color (see Dennett 1991). A possible and common response is to simply doubt these claims. But, in any case, it is not clear that these claims undermine the knowledge argument. One may respond along the following lines: If Mary when first confronted with red were able to conclude that she is now seeing what people call red, she thereby acquires a large set of new beliefs about red experiences (that they are produced by roses, such-and-such wavelength combinations and so on). On the basis of seeing red she (a) acquires a new phenomenal concept of red and (b) she forms new beliefs involving that new concept using her previously acquired physical knowledge. But if this description is correct, then her previous knowledge was incomplete (for a detailed discussion of Dennett’s argument involving the blue banana trick see Dale 1995).