'Slight errors are magnified over time'

Mr. Wingo has now persuaded NASA to use the Deep Space Network to pinpoint ISEE-3's trajectory, to calculate the rocket burn required to put it on a path to Earth orbit. Dr. Farquhar's 1986 calculations were close, but not exact. Slight errors are magnified over time, and now the uncertainty is 20,000 miles, which means the spacecraft could be on course to splat into the moon.

—"Calling Back a Zombie Ship From the Graveyard of Space," by Kenneth Chang, The New York Times, A21, Sunday, June 15, 2014

'all approximations are rational'

...it is obvious that irrationals are uninteresting to an engineer, since he is concerned only with approximations, and all approximations are rational.

—G.H. Hardy, A Mathematician's Apology (1940)

'one must do the whole evil'

'When one does evil one must do the whole evil. To be only half a monster is insanity! There is ecstasy in an extreme of crime.'

—Claude Frollo in Victor Hugo's Notre-Dame of Paris (1831) (trans. John Sturrock 1978)

...he had considered perfectionism...

Even as a young man, to be sure, he had considered perfectionism the basis and most intimate essence of his talent, and for its sake he had curbed and cooled his emotions, because he knew that emotion inclines one to satisfaction with a comfortable approximation, a half of a perfection.

—Thomas Mann, Death in Venice (1912) (trans. Clayton Koelb 1994).

Whatever we want to convey...

Whatever we want to convey, there is only one word to express it, one verb to animate it, one adjective to qualify it. We must therefore go on seeking that word, verb or adjective until we have discovered it, and never be satisfied with approximations, never fall back on tricks, even inspired ones, or tomfoolery of language to dodge the difficulty.

—Guy de Maupassant, "The Novel," preface to Pierre and Jean (1888) (trans. Leonard Tancock 1979).