John Adams was the second president of the United States, having earlier served as the first vice president of the United States. An American Founding Father, Adams was a statesman, diplomat, and a leading advocate of American independence from Great Britain. Well educated, he was an Enlightenment political theorist who promoted republicanism, as well as a strong central government, and wrote prolifically about his often seminal ideas—both in published works and in letters to his wife and key adviser Abigail Adams. Adams was a lifelong opponent of slavery, having never bought a slave. In 1770 he provided a principled, controversial, and successful legal defense to the British soldiers accused in the Boston Massacre, because he believed in the right to counsel and the "protect of innocence".