Extended excerpt [Letter to Richard C. Anderson, U.S. State Department. Italics original to cited text.]:

“Civil liberty can be established on no foundation of human reason which will not at the same time demonstrate the right of religious freedom; and the control of a Bishop of Rome and a conclave of cardinals on the banks of the Tiber over the freedom of action of American nations on the shores of the Orinoco, or the Magdalena, is as incompatible with their independence, as the arbitrary mandate of a Spanish monarch and a Council of the Indies at Madrid. The tendency of the spirit of the age is so strong towards religious liberty, that we cannot doubt it will soon banish from the constitutions of the southern republics of this hemisphere all those intolerant religious establishments with which they have hitherto been trammeled.” (p. 466)

Source link: The Writings of John Quincy Adams, Vol. VII (1917) online via Google Books: https://books.google.com/books?id=WWNHAQAAMAAJ&pg=PA466&lpg=PA466&dq=john+quincy+adams+%2B+Civil+liberty+can+be+established+on+no+foundation+of+human+reason+which+will+not+at+the+same+time+demonstrate+the+right 

Extended excerpt [Speech – modern spelling is cited in quote & excerpt, original text of quote appears as: “Courage and perſeverance have a magical taliſman, before which difficulties diſappear and obſtacles vaniſh into air.”]:

“Courage and perseverance have a magical talisman, before which difficulties disappear and obstacles vanish into air. These qualities have ever been displayed in their mightiest perfection as attendants in the retinue of strong passions.” (p. 13)

Source link: An Oration, Delivered at Plymouth, at the Anniversary Commemoration of the First Landing of Our Ancestors, at That Place (22 December 1802) online via Internet Archive: https://archive.org/details/orationdelivered00ada

Extended excerpt [Per the MA Historical Society footnotes, “In the speech which follows, JQA’s second before the A.B. Club, paragraphing has been editorially supplied.” Speech text from Diary of John Quincy Adams.]:

“The advantages which are derived from Education is one of the most important subjects that can engage the attention of mankind; a subject on which the welfare of states and empires, as well as of small societies, and of individuals in a great measure depends. It has long been an opinion generally received, that the Situation which should afford the greatest degree of happiness to mankind, would be the most eligible; and the Poet appears to be of this Opinion when he says

“For forms of government let fools contest

Whate’er is best administer’d is best.”

Source link: Diary of John Quincy Adams, Vol. 2 (26 June 1786) online via Massachusetts Historical Society: https://www.masshist.org/publications/apde2/view?id=ADMS-03-02-02-0001-0004-0026#DQA02d104n1

Misattribution note: The John Quincy Adams quote “To believe all men honest…” has been incorrectly attributed by some sources to his father (and fellow U.S. president), John Adams.

Extended excerpt [Letter to U.S. Secretary of War William Eustis]:

“All men profess honesty as long as they can. To believe all men honest, would be folly. To believe none so, is something worse.” (pp. 318-319)

Source link: The Writings of John Quincy Adams, Vol. III (1914) online via Google Books: https://books.google.com/books?id=5V5HAQAAMAAJ&pg=PA319&dq=To+believe+all+men+honest+would+be+folly+To+believe+none+so+is+something+worse

Extended excerpt [Adams, referencing a donation left to the United States by James Smithson of London, “for the purpose of founding at Washington an establishment, under the name of the Smithsonian Institution, for the increase and diffusion of knowledge among men…”]:

“To furnish the means of acquiring knowledge is, therefore, the greatest benefit that can be conferred upon mankind. It prolongs life itself, and enlarges the sphere of existence. The earth was given to man for cultivation – to the improvement of his own condition.” (p. 79, column 2)

Source note: For more information on Smithson’s gift to the U.S. – and the reason that John Quincy Adams had to actively advocate for America to graciously receive the funds – see “When Congress Looked James Smithson’s Gift Horse in the Mouth” (30 July 2015) Pamela M. Henson, The Smithsonian: https://www.smithsonianmag.com/smithsonian-institution/looking-james-smithsons-gift-horse-mouth-180956107/

Source link: Register of Debates in Congress, Comprising the Leading Debates and Incidents of the First Session of the Twenty-Fourth Congress, Vol. XII (1836) online via Google Books: https://books.google.com/books?id=GJA_AQAAMAAJ&pg=PA79&lpg=PA79&dq=To+furnish+the+means+of+acquiring+knowledge+is,+therefore,+the+greatest+benefit+that+can+be+conferred+upon+mankind.+It+prolongs+life+itself