“Suppose that we carry a magnetic compass about in the neighbourhood of powerful magnets. The needle waggles as we move and comes to rest pointing in a new direction whenever we stand still in a new position.

“Suppose that instead of a single compass we carry an arrangement of many magnetic needles, large and small, swung so that they influence one another, some able only to swing horizontally, others vertically, others hung freely. As we move, the perturbations in this system will be very complicated. But for every position in which we place it there will be a final position of rest for all the needles into which they will in the end settle down, a general poise for the whole system. But even a slight displacement may set the whole assemblage of needles busily readjusting themselves.

“One further complication. Suppose that while all the needles influence one another, some of them respond only to some of the outer magnets among which the system is moving. The reader can easily draw a diagram if his imagination needs a visual support.

“The mind is not unlike such a system if we imagine it to be incredibly complex. The needles are our interests, varying in their importance, that is in the degree to which any movement they make involves movement in the other needles. Each new disequilibrium, which a shift of position, a fresh situation, entails, corresponds to a need; and the wagglings which ensue as the system rearranges itself are our responses, the impulses through which we seek to meet the need.

“Often the new poise is not found until long after the original disturbance. Thus states of strain can arise which last for years.”

from Science and Poetry by I. A. Richards, 1926