What is an emotion?

In 1884, William James, the American psychologist, famously posed the question: what is an emotion? After more than a century of scientific inquiry, however, emotions remain essentially contested concepts: scientists disagree on how they should be defined, on where to draw the boundaries for what counts as an emotion and what does not, on whether conscious experiences are central or epiphenomenal, and so on. Such disputes have sown great discord...