Yet this paper began the controversy and resistance from the mathematical community, which never abated and caused Cantor much mental stress. The strongest resistance was from his old teacher, Kronecker, who was an influential professor at Berlin and had a large following.
Kronecker didn't even believe in the existence of the real numbers. He believed that, "God made the integers. All the rest is the work of man." He went out of his way to make life difficult for Cantor, including blocking his application for a professorship at Berlin, and seeing to it that some of his papers were rejected from publication.
"My theory stands as firm as a rock; every arrow directed against it will return quickly to its archer.
"How do I know this? Because I have studied it from all sides for many years; because I have examined all objections which have ever been made against the infinite numbers; and above all because I have followed its roots, so to speak, to the first infallible cause of all created things."
— Georg Cantor