“They stand not aloof with the gaping vacuity of vulgar ignorance, nor bend with the cringe of sycophantic insignificance. The graceful pride of truth knows no extremes, and preserves, in every latitude of life, the right-angled character of man.”

Part IV, Prop. LV
Ethics (1677)

Part I : Ambiguity and Freedom
The Ethics of Ambiguity (1947)
Context: In spite of so many stubborn lies, at every moment, at every opportunity, the truth comes to light, the truth of life and death, of my solitude and my bond with the world, of my freedom and my servitude, of the insignificance and the sovereign importance of each man and all men. There was Stalingrad and there was Buchenwald, and neither of the two wipes out the other. Since we do not succeed in fleeing it, let us therefore try to look the truth in the face. Let us try to assume our fundamental ambiguity. It is in the knowledge of the genuine conditions of our life that we must draw our strength to live and our reason for acting [C'est dans la connaissance des conditions authentiques de notre vie qu'il nous faut puiser la force de vivre et des raisons d'agir].

Source: Mathematics as an Educational Task (1973), p. 476-477

Letter to Roger C. Weightman http://www.rjgeib.com/thoughts/jefferson/jefferson.html, declining to attend July 4th ceremonies in Washington D.C. celebrating the 50th anniversary of Independence, because of his health. This was Jefferson's last letter http://www.rjgeib.com/thoughts/jefferson/jefferson.html. (24 June 1826)
1820s
Context: All eyes are opened, or opening, to the rights of man. The general spread of the light of science has already laid open to every view the palpable truth, that the mass of mankind has not been born with saddles on their backs, nor a favored few booted and spurred, ready to ride them legitimately, by the grace of God. These are grounds of hope for others. For ourselves, let the annual return of this day forever refresh our recollections of these rights, and an undiminished devotion to them.

Congressional speech (1849)
Context: I affirm, in words as true and literal as any that belong to geometry, that the man who withholds knowledge from a child not only works diabolical miracles for the destruction of good, but for the creation of evil also. He who shuts out truth, by the same act opens the door to all the error that supplies its place. Ignorance breeds monsters to fill up all the vacuities of the soul that are unoccupied by the verities of knowledge. He who dethrones the idea of law, bids chaos welcome in its stead. Superstition is the mathematical complement of religious truth; and just so much less as the life of a human being is reclaimed to good, just so much more is it delivered over to evil. The man or the institution, therefore, that withholds knowledge from a child, or from a race of children, exercises the awful power of changing the world in which they are to live, just as much as though he should annihilate all that is most lovely and grand in this planet of ours, or transport the victim of his cruelty to some dark and frigid zone of the universe, where the sweets of knowledge are unknown, and the terrors of ignorance hold their undisputed and remorseless reign.

14 December 1756
Letters to His Son on the Art of Becoming a Man of the World and a Gentleman (1774)

Source: All I Really Need to Know I Learned in Kindergarten

Source: Dictionary of Burning Words of Brilliant Writers (1895), P. 294.