Physics and Common Sense

Modern mathematical physics began in open defiance of common sense. Galileo declared – through his spokesman Salviati – that he could not “sufficiently admire the outstanding acumen” of the heliocentrist astronomers, who, “through sheer force of intellect,” had “done such violence to their own senses as to prefer what reason told them over that which sensible experience plainly showed them to the contrary” (EN VII, 355; Drake translation). Furthermore, he judged color and sound, heat and cold to be mere affections of the human senses, like the tickling one feels when a feather is introduced into one's nose, which, of course, lies not on the feather but on the nerves stimulated by it (1623, §48). The most conspicuous features by which we perceive and classify in everyday life the objects that surround us were thus pronounced mind-dependent or “subjective” and banished from the stock of notions that the new physics would employ to describe and understand the real, “objective” nature of things. Physical discourse retained many terms from ordinary language – arithmetic terms familiar in housekeeping and trade; geometric terms developed in carpentry, architecture, and land-surveying; chronometric terms used in lithurgy, seafaring, and, increasingly since the Renaissance, also in daily business; terms applicable to machines found in harbors and building sites –, which physicists sought only to define better and to apply with greater precision.