By the "mud-sill" theory it is assumed that labor and education are incompatible; and any practical combination of them impossible. According to that theory, a blind horse upon a tread-mill, is a perfect illustration of what a laborer should be—all the better for being blind, that he could not tread out of place, or kick understandingly.... Free labor insists on universal education.
Abraham Lincoln (1809–1865), U.S. president. address before the Wisconsin State Agricultural Society, Milwaukee, Wisconsin, Sep. 30, 1859. Collected Works of Abraham Lincoln, vol. 3, p. 479, Rutgers University Press (1953, 1990).