interracial, common-law marriages with slaves (see Partus sequitur ventrem). Justifications in the South "A necessary evil" In the 19th century, proponents of slavery often defended the institution as a "necessary evil". At that time, it was feared that emancipation of black slaves would have more harmful social and economic consequences than the continuation of slavery. On April 22, 1820, Thomas Jefferson, one of the Founding Fathers of the United States, wrote in a letter to John Holmes, that with slavery, The French writer and traveler Alexis de Tocqueville, in his influential Democracy in America (1835), expressed opposition to slavery while observing its effects on American society. He felt that a multiracial society without slavery was untenable, as he believed that prejudice against blacks increased as they were granted more rights (for example, in northern states). He believed that the attitudes of white Southerners, and the concentration of the black population in the South, were bringing the white and black populations to a state of equilibrium, and were a danger to both races. Because of the racial differences between master and slave, he believed that the latter could not be emancipated. In a letter to his wife dated December 27, 1856, in reaction to a message from President Franklin Pierce, Robert E. Lee wrote, "A positive good" However, as the abolitionist movement's agitation increased and the area developed for plantations expanded, apologies for slavery became more faint in the South. Leaders then described slavery as a beneficial scheme of labor management. John C. Calhoun, in a famous speech in the Senate in 1837, declared that slavery was "instead of an evil, a gooda positive good". Calhoun supported his view with the following reasoning: in every civilized society one portion of the community must live on the labor of another; learning, science, and the arts are built upon leisure; the African slave, kindly treated by his master and mistress and looked after in his old age, is better off than the free laborers of Europe; and under the slave system conflicts between capital and labor are avoided. The advantages of slavery in this respect, he concluded, "will become more and more manifest, if left undisturbed by interference from without, as the country advances in wealth and numbers". South Carolina army officer, planter and railroad executive James Gadsden called slavery "a social blessing" and abolitionists "the greatest curse of the nation". Gadsden was