  Qualia inversion thought experiments are ubiquitous in contemporary philosophy of mind (largely due to the influence of Shoemaker 1982 and Block 1990). The most popular kind is one or another variant of Locke’s hypothetical case of “spectrum inversion”, in which strawberries and ripe tomatoes produce visual experiences of the sort that are actually produced by grass and cucumbers, grass and cucumbers produce experiences of the sort that are actually produced by strawberries and ripe tomatoes, and so on. This entry surveys the main philosophical applications of what Dennett has called “one of philosophy’s most virulent memes” (1991, 389).