Those who lay stress on the unity of mind regard it as almost evident a priori, that but one concept can occupy the focus of attention at a time... Attention, like the lens of the eye, is now [ie, first] accommodated to act as an instrument of near focus, high magnification, but limited aperture, and again [then] as one of distant focus, small magnifying-power, but wide range
Can the Mind attend to two things at once? Science: July 18, 1887
