[The infinitely small] neither have nor can have theory; it is a dangerous instrument in the hands of beginners [. . . ] anticipating, for my part, the judgement of posterity, I would dare predict that this method will be accused one day, and rightly, of having retarded the progress of the mathematical sciences.
All times are beautiful for those who maintain joy within them; but there is no happy or favorable time for those with disconsolate or orphaned souls.