Thomas Jefferson on a free black man

Nature or “nurture”?
We have now in the United States a negro [Benjamin Banneker], the son of a black man born in Africa, and a black woman born in the United States, who is a very respectable mathematician. I procured him to be employed under one of our chief directors in laying out the new Federal city on the Potomac, and in the intervals of his leisure, while on that work, he made an almanac for the next year, which he sent me in his own handwriting, and which I enclose to you. I have seen very elegant solutions of geometrical problems by him. Add to this that he is a very worthy and respectable member of society. He is a free man. I shall be delighted to see these instances of moral eminence so multiplied as to prove that the want of talents, observed in them, is merely the effect of their degraded condition, and not proceeding from any difference in the structure of the parts on which intellect depends.
Thomas Jefferson to Marquis De Condorcet, 1791, 744

Patrick Lee’s Explanation
In his book, Notes on Virginia, written nine years earlier, Jefferson noted a number of limitations among  his servants at Monticello. Banneker was unlike any of them. Seeing Banneker’s potential, Jefferson provided for his employment in the design of the new national capital, Washington City.
Jefferson hoped to see more talented people like this surveyor and mathematician, as proof that any weaknesses among the African race stemmed from the degradation of slavery and not on any natural limitations.