In 1701 he stirred his section by publishing his _Selling of Joseph_, a distinctly anti-slavery pamphlet, based on the natural and inalienable right of every man to be free.[1] The appearance of this publication marked an epoch in the history of the Negroes.

It was the first direct attack on slavery in New England.

The Puritan clergy had formerly winked at the continuation of the institution, provided the masters were willing to give the slaves religious instruction.

In the _Selling of Joseph_ Sewall had little to say about their mental and moral improvement, but in the _Athenian Oracle_, which expressed his sentiments so well that he had it republished in 1705,[2] he met more directly the problem of elevating the Negro race.

Taking up this question, Sewall said: "There's yet less doubt that those who are of Age to answer for themselves would soon learn the Principles of our Faith, and might be taught the Obligation of the Vow they made in Baptism, and there's little Doubt but Abraham instructed his Heathen Servants who were of Age to learn, the Nature of Circumcision before he circumcised them; nor can we conclude much less from God's own noble Testimony of him, 'I know him that he will command his Children and his Household, and they shall keep the Way of the Lord.'"[3] Sewall believed that the emancipation of the slaves should be promoted to encourage Negroes to become Christians.