- It costs so much to be a full human being that there are very few who have the enlightenment, or the courage, to pay the price…. One has to abandon altogether the search for security, and reach out to the risk of living with both arms. One has to embrace the world like a lover, and yet demand no easy return of love. One has to accept pain as a condition of existence. One has to court doubt and darkness as the cost of knowing. One needs a will stubborn in conflict, but apt always to the total acceptance of every consequence of living and dying.
- The Shoes of the Fisherman (1963)
- I can write no more today. The contemplation of my sorry state has reduced me to so deep a melancholy that I contemplate opening my wrist like Petronius Arbiter and lapsing quietly into oblivion. Unlike Petronius, however, I shall have neither the sound of music nor the gentle talk of friends. I still have time to choose a better moment — besides, who knows to what nightmares I might awake.
- Last lines which he had written for his unfinished work The Last Confession (2000), about the last days of Giordano Bruno.
The Heretic (1968) 
- A play in three acts on the arrest, imprisonment, and trials of Giordano Bruno who was burned at the stake in 1600.
- There are a few of us — madmen all! — who are in love with knowing, who would sell the last shirt from our backs for one small truth, one tiny star-fire to light up the murk and mystery of what we call our life… We may go blind before we see it, that's the haunting —
- No man — prince, peasant, pope, — has all the light, who says else is a mountebank. I claim no private lien on truth, only a liberty to seek it, prove it in debate, and to be wrong a thousand times to reach a single rightness. It is that liberty they fear. They want us to be driven to God like sheep, not running to him like lovers, shouting joy!"
- Ever since the Greeks, we have been drunk with language! We have made a cage with words and shoved our God inside!
- If God be God and man a creature made in image of the divine intelligence, his noblest function is the search for truth.
- O Mother of Christ, who saw what men could do to one who heard an alien music! Bend to me, be tender. I am blind and deaf and dumb. And yet I do see visions, shout a kind of praise, feel in my pulse apocalyptic drums.
- I wonder how it will read five hundred years from now? — To make a man confess a loving God you burn him!
- To make that long, last donkey-ride between the pikeman and the stake, to hear the shouting and the chant of hypocrites, to be a spectacle for animals in human masks!
- You I admire as being more, — much more — a man, and more believer too, than half the canting orthodox.
- I'm a Nolan. I could dazzle you in dialect, because the words do not make the same sense to different men.
- Who said to me, a foetus in the womb, a puling babe, "You have your life, but on the condition that you thus believe?" No one! Not even God! So gentlemen, I say you have no right to make terms for my life. I tell you then — No! I will not recant.
The Clowns of God (1981) 
- Once you accept the existence of God — however you define him, however you explain your relationship to him — then you are caught forever with his presence in the center of all things. You are also caught with the fact that man is a creature who walks in two worlds and traces upon the walls of his cave the wonders and the nightmare experiences of his spiritual pilgrimage.
- "Forbear to ask what tomorrow may bring" … If you spend your whole life waiting for the storm, you'll never enjoy the sunshine.
- This statement begins with a quotation of Horace.