given credit for, including being the first to present an epsilon argument.

In his 1821 book [[Cours d'analyse]], Augustin-Louis Cauchy discussed variable quantities, infinitesimals and limits, and defined continuity of by saying that an infinitesimal change in necessarily produces an infinitesimal change in , while Grabiner claims that he used a rigorous epsilon-delta definition in proofs. In 1861, Karl Weierstrass