Twofold Mistake Quotes

“Berkeley explained that by finding the tangent by means of differentials, one first assumes increments; but these determine the secant, not the tangent. One undoes this error, however, by neglecting higher differentials, and thus "by virtue of a twofold mistake you arrive, though not at science, yet at the truth.”
― Carl B. Boyer, The History of the Calculus and Its Conceptual Development