Qualia and Externalism
We have examined content externalism: it is about representational contents. Content externalists think of the mind as representing the world through representational contents individuated by the world. What makes my thought now—that there is a glass of water in front of me—a thought about water is my history of encounters with water and glasses. How might a content externalist try to account for subjective experience—what externalists think of as phenomenal properties? A content externalist needs to find a way of explaining them in terms of representational contents and then show how those representational contents can be differentiated by the world.
A common idea is this: we can think of conscious experience as having representational and phenomenal properties. The phenomenal properties may seem different from representational properties, but content externalists argue that they are not. We use different vocabulary when we talk about phenomenal properties in comparison with when we talk about other representational properties but all the same, phenomenal properties are representational properties. People may think representational properties are insufficient for qualia, but they are wrong. Phenomenal properties reduce to representational ones. Let us go through an example. As I look at the sun, I have an experience of a round yellow object. My experience has the representational properties of round and yellow. We can also say it has phenomenal properties of “yellowness” and “roundness.” But what are these things if not yellow and round representational properties? These properties are, in turn, individuated by the sun.
This way of looking at phenomenal properties can be thought of as the strong version of representationalism. Phenomenal properties reduce to representational properties. Phenomenal properties have no separate ontological status: all there is to conscious experience is representation. Some externalists believe this version of representationalism does not do justice to phenomenal properties.
There is a weaker version in which phenomenal properties supervene upon representational properties. In this version, there is something irreducible about the phenomenal character of our experience. So when I look at the sun, the yellowness and roundness I experience fail reduction to yellow and round representational properties, but they supervene upon those properties.
The sun individuates my phenomenal properties, since they supervene upon representational properties of yellow and round, and those properties represent properties of the sun. But what does it mean for phenomenal properties to supervene upon representational properties? Block tries to show that qualia (phenomenal properties) cannot be explained in terms of representational properties through another Twin Earth-style thought experiment.