In the blink of an eye, I can redirect my thought from London to Cairo, from cookies to unicorns, from former President Obama to the mythical flying horse, Pegasus. How is this possible? How can we think about things that do not exist, like unicorns and Pegasus? Thinking About Things addresses these and related questions, taking as its framework a representational theory of mind. It explains how mental states are attributed, what their aboutness consists in, whether or not they are relational, and whether any of them involve nonexistent things like unicorns. The explanation centers on display theory, a theory of what is involved in attributing attitudes like thinking, hoping, and wanting. These attributions are intensional: some of them seem to involve nonexistent things, and they typically have semantic and logical peculiarities, like the fact that one cannot always substitute one expression for another that refers to the same thing without affecting truth. Display theory explains away these seeming anomalies. For example, substituting coreferring expressions does not always preserve truth because the correctness of an attribution depends on what concepts it displays, not on what the concepts refer to. And a concept that refers to nothing may be used in an accurate display of what someone is thinking. The book describes how concepts can be learned, originated, and given a systematic semantic description, independently of whether there exist things to which they refer. There being no things we are thinking about does not mean that we are not thinking about things.
