Intellect is not sexed;... strength of mind is not sexed; and … our views about the duties of men and the duties of women, the sphere of man and the sphere of woman, are mere arbitrary opinions, differing in different ages and countries, and dependent solely on the will and judgment of erring mortals.

Letter 9 (August 25, 1837). - Letters on the Equality of the Sexes and the Condition of Woman (1853)