"I was gazing toward the Circus Maximus, toward the Palatine Hill where the Roman emperors once resided and reigned and looked down upon the persecution of Christians, and I thought, ‘Where are their successors? Where is the successor of Caesar Augustus? Where is the successor of Marcus Aurelius? And finally, who cares? But if you want to see the successor of Peter, he is right next to me, smiling and waving at the crowds."

Cardinal Francis George

"All human conflict is ultimately theological."

Cardinal Henry Edward Manning, quoted in Hilaire Belloc's The Cruise of Nona

Christians are, moreover, born for combat, whereof the greater the vehemence, the more assured, God aiding, the triumph: "Have confidence; I have overcome the world." (John 16:33)

Pope Leo XIII, Sapientiae Christianae

"Constantly wrestle with your thought, and whenever it wanders call it back to you."

St. John Climacus, The Ladder of Divine Ascent 4.92

"The saint is a medicine because he is an antidote. Indeed that is why the saint is often a martyr; he is mistaken for a poison because he is an antidote. He will generally be found restoring the world to sanity by exaggerating whatever the world neglects, which is by no means always the same element in every age. Yet each generation seeks its saint by instinct; and he is not what the people want, but rather what the people need [...] Therefore it is the paradox of history that each generation is converted by the saint who contradicts it most.”

GK Chesterton, St. Thomas Aquinas, Chapter 1

"Men do not differ much about what things they will call evils; they differ enormously about what evils they will call excusable."

GK Chesterton, Illustrated London News, 1909

"The sort of man who admires Italian art while despising Italian Religion is a tourist and a cad."

GK Chesterton, Roman Converts, Dublin Review, 1925

There is a well-known story about the novelist Evelyn Waugh. He was once very rude and his hostess remonstrated: “How can you behave so badly – and you a Catholic!” Waugh replied: “You have no idea how much nastier I would be if I was not a Catholic. Without supernatural aid I would hardly be a human being.” We remember this riposte both because it is redolent of Waugh’s mordant humour and because it reminds us that, without grace, we would all “hardly be a human being."

Francis Phillips

"A Catholic is a person who has plucked up courage to face the incredible and inconceivable idea that something else may be wiser than he is."

GK Chesterton, The Surrender on Sex, 1934

"My brother, give yourself to God before death comes upon you. Detach yourself instantly from everything which removes, or can remove, you from God. Let us instantly renounce the goods of this earth, before death strips us of them by force."

St. Alphonsus Liguori, Preparation for Death, pg. 23

"For surely our whole life is involved in a constant battle in which our salvation itself is at stake; nothing is more disgraceful for a Christian than cowardice."

Pope Leo XIII, Inimica Vis (7)

"For heresies, and certain tenets of perversity, ensnaring souls and hurling them into the deep, have not sprung up except when good Scriptures are not rightly understood, and when that in them which is not rightly understood is rashly and boldly asserted."

St. Augustine, Treatise 18 on John 5

"The devil also speaks about Scripture, and all the heresies, according to Ezekiel [13:18], take material from it and sew together pillows which they place under the elbow of every age. As for me, when I have Christ in me as I speak, I do not have the gospel of man. [...] Great harm is done to the Church when by means of some perverse interpretation the Gospel of Christ turns into the gospel of man—or, what is worse, the gospel of the devil."

St. Jerome, Commentary on Galatians 1:11-12

"In truth, sudden uprisings and the boldest rebellions immediately followed in Germany the so-called Reformation,[referring to the German Peasants' Revolt] the authors and leaders of which, by their new doctrines, attacked at the very foundation religious and civil authority; and this with so fearful an outburst of civil war and with such slaughter that there was scarcely any place free from tumult and bloodshed. From this heresy there arose in the last century a false philosophy — a new right as it is called, and a popular authority, together with an unbridled license which many regard as the only true liberty. Hence we have reached the limit of horrors, to wit, communism, socialism, nihilism, hideous deformities of the civil society of men and almost its ruin."

Pope Leo XIII, Diuturnum (23)

“Read assiduously and learn as much as you can. Let sleep find you holding your Bible, and when your head nods let it be resting on the sacred page.”

St. Jerome, Letter 22 To Eustochium (17)

Q: Who, besides apostates and heretics, sin against the Faith?

A: Besides apostates and heretics, the following sin against the Faith:
i. unbaptized people who repudiate the faith after it has been sufficiently clearly put before them—this is “positive infidelity” ;
ii. people who neglect to secure sufficient religious instruction such as suits their age and condition in life ;
iii. people who embrace errors condemned by the Church and which approximate more or less to heresy ;
iv. people who deliberately expose themselves to the danger of losing their faith—those, for example, who without leave and due precautions read books prohibited by the Church, especially books written by apostates, heretics or schismatics in defense of their apostasy, heresy or schism.

The 1932 Catholic Catechism, 523

November 27, 1095

"Oh, race of Franks, race from across the mountains, race chosen and beloved by God, as shines forth in very many of your works set apart from all nations by the situation of your country, as well as by your Catholic Faith and the honor of the Holy Church!
From the confines of Jerusalem and the city of Constantinople a horrible tale has gone forth... that a race from the kingdom of the Persians, an accursed race... has invaded the lands of those Christians and has depopulated them by the sword, pillage and fire...
Let the deeds of your ancestors move you and incite your minds to manly achievements; the glory and greatness of King Charles the Great and of your other kings... Oh, most valiant soldiers and descendants of invincible ancestors, be not degenerate, but recall the valor of your progenitors...
Accordingly undertake this journey for the remission of your sins, with the assurance of the imperishable glory of the Kingdom of Heaven."

Bl. Urban II's Speech at Clermont

Sorry this is so spliced, the character limit's 1024 with media. The entire speech is worth reading, would highly recommend!

"So vast is the number of heretics and so great their diversity in dogma, that, though among themselves they differ greatly in opinions and doctrines, in their hatred of us, they are of one accord. Just as Herod and Pilate, for example, who were enemies, made their peace in persecuting Christ, and were more formidable in their amity than their enmity, so the heretics, impiously at variance, league together for still greater impiety."

St. Jerome, Homilies on the Psalms: Homily 62, Psalm 82

"It is the hope and prayer of all of us who profess the Catholic Faith that heresy be refuted and individuals be converted. Or, if they choose to persist in error, the blame is certainly not to be placed on us…, but rather on those who have preferred falsehood to truth."

St. Jerome, The Dialogue Against the Pelagians, Book I, Preface, paragraph 2

"Heretics are never constant in their convictions, but are forever changing their opinions, shifting back and forth."

St. Jerome, Homilies on the Psalms: Homily 68, Psalm 90