Feminism is the belief that women should have social, political and economic equality with men. There have been many different movements based on different variations of this central tenet, and in modern theory, the evolution of femism is often organized loosely into three "waves": the first wave was during the late 19th and early 20th centuries, beginning with the activities of women in the anti-slavery movement (particularly the Seneca Falls Convention held in 1848) and ending with the passage of the 19th Amendment to the United States Constitution in 1920, which gave American women the right to vote. The second wave is identified with the "baby boom" generation of the 1960's and 70's. Two seminal works that inspired this generation of feminists were Simone de Beauvoir's work The Second Sex (1949) and Betty Friedan's The Feminine Mystique (1963). The third wave of feminism is considered to be women who came of age in the 80's and 90's and had been influenced by postmodernism.