What were the reasons behind Jefferson''s reservations over the purchase of Louisiana, and how was he able to reason these doubts away?

Jefferson advocated strict adherence to the U. S. Constitution and there were no provisions within the Constitution to permit the U. S.' purchase of new territory. However, because of wide popular support for the purchase of the new territory as well as the value the territory would bring to the newly formed United States Jefferson decided to forgo the legalistic view of the Constitution and supported the purchase of the territory.