Some have objected to Jackson's argument on the grounds that the scenario described in the thought experiment itself is not possible. For example, Evan Thompson questioned the premise that Mary, simply by being confined to a monochromatic environment, would not have any color experiences, since she may be able to see color when dreaming, after rubbing her eyes, or in afterimages from light perception. However, Graham and Horgan suggest that the thought experiment can be refined to account for this: rather than situating Mary in a black and white room, one might stipulate that she was unable to experience color from birth, but was given this ability via medical procedure later in life. Nida-Rümelin recognizes that one might question whether this scenario would be possible given the science of color vision (although Graham and Horgan suggest it is), but argues it is not clear that this matters to the efficacy of the thought experiment, provided we can at least conceive of the scenario taking place.