Karl Theodor Wilhelm Weierstrass was a German mathematician often cited as the "father of modern analysis". Despite leaving university without a degree, he studied mathematics and trained as a teacher, eventually teaching mathematics, physics, botany and gymnastics.Weierstrass formalized the definition of the continuity of a function, proved the intermediate value theorem and the Bolzano–Weierstrass theorem, and used the latter to study the properties of continuous functions on closed bounded intervals. Wikipedia
... es ist wahr, ein Mathematiker, der nicht etwas Poet ist, wird nimmer ein vollkommener Mathematiker sein.
Letter to Sofia Kovalevskaya, August 27, 1883, as shared by Gösta Mittag-Leffler at the 2nd International Congress for Mathematicians in Paris. Compte rendu du deuxième Congrès international des mathematiciens tenu à Paris du 6 au 12 août 1900, Gauthier-Villars (Paris), 1902, page 149.
