sentences:  Six of them had been collated into an expensively bound volume titled "Tracts on Slavery", indicating that he attached some importance to that selection.Five of the six were published in or after 1788.All six shared common themes that slaves first had to be educated about the obligations of liberty before they could be emancipated, a belief Washington is reported to have expressed himself in 1798, and that abolition should be realized by a gradual legislative process, an idea that began to appear in Washington's correspondence during the Confederation period.