During the Meiji Restoration, Yukichi immediately introduced feminism of Western countries to Japan; he stated that polygyny and the keeping a mistress are bad practices because 'the married couple is the base of morality', that women should be emancipated, and that women should be granted the right to receive an equal education because women and men are equally human beings.
福澤は、明治維新になって欧米諸国の女性解放思想をいちはやく日本に紹介し、「人倫の大本は夫婦なり」として一夫多妻制や妾をもつことを非難し、女性にも自由を与えなければならぬとし、女も男も同じ人間だから、同様の教育を受ける権利があると主張した。