Can a free government possibly exist with the Roman Catholic religion?

{Letter to Thomas Jefferson, May 19, 1821}

I almost shudder at the thought of alluding to the most fatal example of the abuses of grief which the history of mankind has preserved - the Cross. Consider what calamities that engine of grief has produced! With the rational respect that is due to it, knavish priests have added prostitutions of it, that fill or might fill the blackest and bloodiest pages of human history.

{Letter to Thomas Jefferson, September 3, 1816]

I am bold to Say that neither you nor I, will live to See the Course which 'the Wonders of the Times' will take. Many Years, and perhaps Centuries must pass, before the current will acquire a Settled direction... yet Platonic, Pythagoric, Hindoo, and cabalistic Christianity, which is Catholic Christianity, and which has prevailed for 1,500 years, has received a mortal wound, of which the monster must finally die. Yet so strong is his constitution, that he may endure for centuries before he expires.

{Letter to Thomas Jefferson, July 16 1814}

This society [Jesuits] has been a greater calamity to mankind than the French Revolution, or Napoleon's despotism or ideology. It has obstructed the progress of reformation and the improvement of the human mind in society much longer and more fatally.

{Letter to Thomas Jefferson, November 4, 1816. Adams wrote an anonymous 4 volume work on the destructive history of the Jesuits}