Final answer:
John Quincy Adams was the primary architect of the Monroe Doctrine, promoting the idea that the Western Hemisphere should be free from European colonization and interference, while Thomas Jefferson's earlier actions and ideologies contributed to the Doctrine's spirit.
Step-by-step explanation:
Thomas Jefferson and John Quincy Adams both played vital roles in the development of the Monroe Doctrine, which was a cornerstone of American foreign policy. Jefferson, as a former president and influential thinker, may not have directly contributed to its formulation in 1823 but his earlier acquisition of the Louisiana Purchase and his belief in the United States as an emerging power set precedents for the Doctrine's principles. However, it was John Quincy Adams, serving as Secretary of State under President James Monroe, who was the primary architect of the Monroe Doctrine. Adams believed that the Western Hemisphere should be free from future European colonization and that the political systems of the Americas and Europe were inherently different, warranting non-interference in each other's affairs. The Monroe Doctrine was formally introduced in Monroe's annual message to Congress in December 1823 and warned European powers against further colonization and intervention in the Western Hemisphere and marked a significant moment of U.S. diplomatic nationalism and imperial rhetoric.