Qualia are phenomenal properties of sensations and perceptual states: they are whatever it is that gives such states their “felt,” qualitative character. (In speaking of sensations, I speak of course not of mental objects or mental contents, but of mental events—of sensings, not sensa.).

Colours are as objective as shapes. Representationalism about perceptual experiences – the view that perceptual experiences represent that things are thus and so, and that their doing so is at least part of what makes them the kinds of experiences they are – tells us this, and also how to defend the position against the most potent objection to it, the argument from the variability of colour vision.

In practice, scientists must convey data in a “representational style”. Various authors seek to explain the epistemic role of scientific visual representation in terms of formal conventions. Goodman also tends to dismiss the epistemic relevance of human cognition. My position is that visual conventions are nonarbitrary, in that they play to scientists’ cognitive abilities and limitations. My account draws on Perini's formal analysis, scientific case studies, and empirical literature on global pattern detection in neurotypicals, autistics, and dyslexics.

Qualia inversion thought experiments are ubiquitous in contemporary philosophy of mind. The most popular kind is one or another variant of Locke's hypothetical case of.