William James's theory of emotion

Chapter 2 endnote 9, from How Emotions are Made: The Secret Life of the Brain by Lisa Feldman Barrett.
Some context is:

An emotion is your brain’s creation of what your bodily sensations mean, in relation to what is going on around you in the world. Philosophers have long proposed that your mind makes sense of your body in the world, from René Descartes in the seventeenth century to William James (considered the father of American psychology) in the nineteenth; as you will learn, however, neuroscience now shows us how this process ​— ​and much more ​— ​occurs in the brain to make an emotion on the spot.

My experience in the coffee shop—when I constructed a feeling of attraction to my coffee date out of early symptoms of the flu—was typically Jamesian. A stimulus (the influenza virus, not the guy) produced physical changes in my body (feeling flushed and jittery) that I experienced as emotional (attraction). In William James’s view, this is all business as usual. There is no such thing as an “emotional reaction.” There are only “reactions”—heart rate, nervous system activation, facial movements, and so on—some of which we experience as emotions, and many of which we don’t. Your racing heart might mean you’re afraid, or that you just ran up a hill. Your scrunched-up face might mean you feel disgust or just have an itchy nose.

Other philosophers before James had proposed similar ideas that emotions are perceptions of physical states, including Descartes, Spinoza, and Malebranche,, but none had James’s flair. He wrote beautiful prose—as did his brother, the novelist Henry James—and we all know how bewitching and convincing a damn good story can be.

James’s ordering of the emotional sequence may have originated in an early version of Wilhelm Wundt’s ideas about emotion, which can be found in early German editions of The Principles of Physiological Psychology.