What are emotions? To most of us, the question hardly needs asking; emotions are the most immediate, the most self-evident, and the most relevant of our orientations toward life. But from the moment the question is taken seriously, troubling difficulties of definition arise.

Emotions have been compared to colors. Both emotions and colors have a strong subjective or experiential character; that is, it makes sense to individuals to describe the qualities and features of the perceived color or the experienced emotion, sometimes at length. In both cases, there is no way for an independent observer to check these “self-reports.” However, these reported experiential qualities display great constancy from one person to another. Most agree, for example, that pink is a warm color, while blue is cool; most agree that fear brings excitement, rapid thinking, a readiness for action, whereas sorrow is inactive and renders one incommunicative. There is a long-standing common sense that says that both color perception and emotional experience are biologically based and therefore everywhere the same. The experiential qualities individuals report are, by this common sense, universal, “hardwired”; just as sugar always tastes sweet, so pink always looks warm and loneliness always feels cold. But while scientific evidence on color perception supports this commonsense view, research into emotions has failed to substantiate it. This contrast is instructive, a good starting point for appreciating the difficulties into which the concept of “emotion” plunges us.