“Attention is the rarest and purest form of generosity,” Simone Weil wrote. Decades later, cognitive scientist Alexandra Horowitz observed in her marvelous inquiry into our everyday blinders: “Attention is an intentional, unapologetic discriminator. It asks what is relevant right now, and gears us up to notice only that.”

More than a century earlier, in his masterwork The Principles of Psychology, Vol. 1 (public library), pioneering psychologist William James (January 11, 1842–August 26, 1910) examined the interplay of generosity and mercilessness in this greatest of human superpowers, which shapes our basic experience of reality.

James offers a wonderfully precise yet alive definition of attention:

Attention … is the taking possession by the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought, localization, concentration, of consciousness are of its essence. It implies withdrawal from some things in order to deal effectively with others, and is a condition which has a real opposite in the confused, dazed, scatter brained state which in French is called distraction, and Zerstreutheit in German.

Long before contemporary psychologists came to examine the self-referential base of consciousness, James writes:

Millions of items of the outward order are present to my senses which never properly enter into my experience. Why? Because they have no interest for me. My experience is what I agree to attend to. Only those items which I notice shape my mind — without selective interest, experience is an utter chaos. Interest alone gives accent and emphasis, light and shade, background and foreground intelligible perspective, in a word. It varies in every creature, but without it the consciousness of every creature would be a gray chaotic indiscriminateness, impossible for us even to conceive.

It’s a notion at once commonplace and utterly radical for us today — somehow, mesmerized by the glowing rectangles we carry everywhere, we seem to have relinquished this most elemental form of agency shaping our experience of life. There is a striking similarity between James’s vivid description of inattentiveness, predicated on the now-endangered phenomenon of boredom, and the mind-body state induced by the vast majority of our device use, portending to ward off boredom but effecting the very same result:

Most people probably fall several times a day into a fit of something like this: The eyes are fixed on vacancy, the sounds of the world melt into confused unity, the attention is dispersed so that the whole body is felt, as it were, at once, and the foreground of consciousness is filled, if by anything, by a sort of solemn sense of surrender to the empty passing of time. In the dim background of our mind we know meanwhile what we ought to be doing: getting up, dressing ourselves, answering the person who has spoken to us, trying to make the next step in our reasoning… Every moment we expect the spell to break, for we know no reason why it should continue. But it does continue, pulse after pulse, and we float with it, until also without reason that we can discover an energy is given, something we know not what enables us to gather ourselves together, we wink our eyes, we shake our heads, the background-ideas become effective, and the wheels of life go round again. […] The abolition of this condition is what we call the awakening of the attention.

James offers a similarly sobering lens on multitasking. To the question of how many things we can attend to at once — how many “entirely disconnected systems or processes of conception can go on simultaneously” in our consciousness — he answers:

Not easily more than one, unless the processes are very habitual; but then two, or even three, without very much oscillation of the attention. Where, however, the processes are less automatic … there must be a rapid oscillation of the mind from one to the next, and no consequent gain of time. […] When expectant attention is concentrated upon one of two sensations, that the other one is apt to be displaced from consciousness for a moment and to appear subsequent; although in reality the two may have been contemporaneous events.

The act of paying attention and the way in which it is performed, James argues, is what sets geniuses apart from ordinary people:

Sustained attention is the easier, the richer in acquisitions and the fresher and more original the mind. In such minds, subjects bud and sprout and grow. At every moment, they please by a new consequence and rivet the attention afresh. But an intellect unfurnished with materials, stagnant, unoriginal, will hardly be likely to consider any subject long. A glance exhausts its possibilities of interest. Geniuses are commonly believed to excel other men in their power of sustained attention… Their ideas coruscate, every subject branches infinitely before their fertile minds, and so for hours they may be rapt.

But the ultimate measure of genius, James notes in a sentiment that echoes Goethe, isn’t so much the mental style of how attention is paid as the disciplined discernment of what we attend to:

When we come down to the root of the matter, we see that [geniuses] differ from ordinary men less in the character of their attention than in the nature of the objects upon which it is successively bestowed.

The Principles of Psychology, which is in the public domain, remains a foundational text of understanding the human mind. Complement this particular portion with Mary Oliver on what attention really means and Annie Dillard on the two ways of looking, then revisit James on how habit works, what our emotions really are, and the psychology of the second wind.