FIGURE 4.

A way of representing three experiences on a two-dimensional E-space. A pinprick is suggested here as a simple example of tactile experience, disregarding its localization, that can be represented as a point. The sensation of itch might be equally suitable. Sound, for animals that can distinguish frequencies, would be a line from low (L) to high (H) frequency. Color, as we experience it, is a closed curve, as the sequence from red to orange, yellow, green, blue, and violet (R, O, Y, G, B, V) is recursive, leaving the center of the curve for their blended combination, white light. The dotted lines are a reminder that, if these experiences are to be plotted together, there must be a zone of exclusion between them that is devoid of realized experience, as the three experiences would otherwise risk being combined in ways that would render them less distinguishable. The diagram could well have looked quite different if we consider the evolutionary past, how the three qualia originated, and the degree of homology between them. This is shown by the trajectories (arrows from Q1 and Q2). Trajectories originating at Q1 show a route by which a frequency-dependent acoustic experience might have evolved from an ur-quale that originally produced a much more limited range of that experience. Trajectories radiating from Q2 show routes by which an ancestral ur-quale common to multiple mechanosensor-based experiences might have evolved so as to separately evoke sound and tactile sensations, making these homologous as mechanosensations. The trajectories represent sequences of states that have changed over time, but points along the Q2 trajectories are ones that would have been present only in past brains, not present ones, as the SCs responsible for evoking intermediates between the qualia in question would long since have been extinguished by selection. For qualia unrelated through homology as experiences, there may be no such intervening points, and hence no access to intermediate experiences. This could be the case for light and sound for example, which share no obvious qualitative features, in which case there would be no justification for even trying to map them to the same surface. The reader is encouraged to think about how the figure might be used to illustrate the differences between a puddle-like evolutionary sequence and a tree-like one, i.e., to construct an E-space counterpart of Figure 3.