The great fact underlying the claim for universal suffrage is that every man is himself and belongs to himself, and represents his own individuality, not only in form and features, but in thought and feeling. And the same is true of woman. She is herself, and can be nobody else than herself. Her selfhood is as perfect and as absolute as is the selfhood of man.
Source, in full
Speech at the New England Woman Suffrage Association (May 24, 1886) Nicholas Buccola, edit., The Essential Douglass: Selected Writings & Speeches, Hackett Publishing Company, 2016, p. 307. Sometimes referred to as his “Who and What is Woman?” speech