The inverted spectrum scenario is possible: Invert and Nonvert have the same representational properties (the banana looks yellow to both, the strawberries look red to both) despite having different qualia
(The passage presents two competing definitions to contrast the views)
On the Cartesian picture: intrinsic qualities of inner ideas of which subjects are directly aware, necessarily shared by internal duplicates regardless of environment. On wide representationalism: representational contents of inner states whose nature is partly externally determined
Assume that this scenario is possible (for an argument that it isn’t, see Sundström 2002 and Gibbons 2005; for a reply see Littlejohn 2009). The three features just mentioned are intended to support the view that this scenario is one in which, when Invert and Nonvert both look at the fruits depicted in figure 6, their experiences have the same representational properties. In particular (glossing over a complication to be discussed in subsection 3.3 below), the banana looks yellow to both Invert