University Professor, New York University. This Keynote was given at the Conference Fifty Years of Class Actions — A Global Perspective, Fifty Years After the 1966 Amendment of the American Class Action Rule 23, Tel Aviv University, January 4, 2017. I have expanded and updated my lecture, but tried to preserve much of the conversational and personal tone of my presentation at the Conference, but at certain points that did not translate into a written medium. The substance of my remarks has not been changed, however. Citations are designed to be illustrative rather than exhaustive.