"The meaning of the differential equation now follows:\frac{df(t)}{dt} = Af(t)expresses the claim that the rate of change in f(t)... is proportional at t to f(t) itself. And this makes sense. How fast a colony of bacteria will grow is contingent on the... number of bacteria on hand and the relative percentage of bacteria engaged in reproduction. ... Equations are... acts of specification in the dark; something answers to some condition. ...Specification in the dark corresponds to the...process by which a sentence in which a pronoun figures—He smokes—acquires the stamp of specificity when the antecedent... is dramatically or diffidently revealed—Winston Churchill, say, or a lapsed smoker seeking an errant cigarette in a bathroom. The differential equation describing uniform growth admits a simple but utterly general solution by means of the exponential functionf(t) =ke^{At}.The number e is an irrational number lying on the leeward side of the margin between 2 and 3 and playing, like \pi, a strange and essentially inscrutable role throughout all of mathematics; exponentiation takes e to a power... in this case... specified by A and t. The constant k has an interpretation as the problem's initial value... some... (weight or mass) of bacteria. ... as time scrolls backward or forward in the... imagination, ke^{At} provides a running account of growth or decay... This is in itself remarkable, the temporal control achieved by what are after all are just symbols, quite unlike anything else in language or its lore or law, but when successful, specification in the dark achieves an analysis of experience that goes beyond any specific prediction to embrace a universe of possibilities loitering discreetly behind the scenes."