Voltaire, answered from the texts and cited to the page.
Fanaticism is to superstition what delirium is to fever, and what fury is to anger.1 The enthusiast takes his dreams for realities and his imaginings for prophecies; he is a fanatic in embryo, and requires only a step further to become a murderer in the name of God.2 That step is the crucial one. Bartholomew Diaz quit Rome expressly to kill his own brother at Nuremberg — a man guilty of nothing beyond believing that the pope was Antichrist rather than God's vicar — and killed him with piety in his heart.3
Polyeuctes smashed temple ornaments on a feast day. The assassins of Henry III and Henry IV were cut from the same cloth.4 These are not aberrations; they are the doctrine carried to its conclusion. What makes the thing spread is not books but bodies in a room. An ardent man of strong imagination addresses himself to weak imaginations; his eyes dart fire, that fire rapidly spreads, his tones and gestures convulse the nerves of his hearers, and presently they are fighting the battles of the Lord.5
Read in solitude, the same text leaves you cold; hear it shouted by a man whose hands are shaking, and it is a disease as contagious as smallpox.6 Xavier carried his enthusiasm to Japan without knowing a word of Japanese — no matter, the flame caught, a so-called Christendom was formed, and a hundred thousand persons were slaughtered before it was done.7
The coldest fanatics are the worst. The judge who sentences a man to death for thinking differently, without any fever of the moment, without the excuse of madness — he is more guilty than the Clements and the Ravaillacs, precisely because he might have listened to reason and chose not to.8 What is almost never found is reason combined with enthusiasm.
Reason consists in constantly perceiving things as they really are; enthusiasm, by definition, perceives something else entirely.9
Fanaticism is, in reference to superstition, what delirium is to fever, or rage to anger.A Philosophical Dictionary Vol 05
He who is involved in ecstasies and visions, who takes dreams for realities, and his own imaginations for prophecies, is a fanatical novice of great hope and promise, and will probably soon advance to the highest form, and kill man for the love of God.A Philosophical Dictionary Vol 05
Bartholomew, still more ardently convinced that the pope was god upon earth, quits Rome, determined either to convert or murder his brother; he accordingly murdered him!A Philosophical Dictionary Vol 05
The assassins of duke François de Guise, of William, prince of Orange, of king Henry III and king Henry IV, and so many others, were energumens suffering from the same madness as Diaz.Philosophical Dictionary, pp. 199–200
But when an ardent man of strong imagination addresses himself to weak imaginations, his eyes dart fire, and that fire rapidly spreads; his tones, his gestures, absolutely convulse the nerves of his auditors. He exclaims, 'The eye of God is at this moment upon you; sacrifice every mere human possession and feeling; fight the battles of the Lord'--and they rush to the fight.A Philosophical Dictionary Vol 05
It is a malady of the mind, which is taken in the same way as smallpox. Books communicate it much less than meetings and discourses. We seldom get heated while reading in solitude, for our minds are then tranquil and sedate.A Philosophical Dictionary Vol 05
This Christendom ends in a civil war, in which a hundred thousand persons are slaughtered: the enthusiasm then is at its highest point, fanaticism; and fanaticism has become madness.A Philosophical Dictionary Vol 04
There are some cold-blooded fanatics; such as those judges who sentence men to death for no other crime than that of thinking differently from themselves, and these are so much the more guilty and deserving of the execration of mankind, as, not laboring under madness like the Clements, Châtels, Ravaillacs, and Damiens, they might be deemed capable of listening to reason.A Philosophical Dictionary Vol 05
What is most rarely to be met with is the combination of reason with enthusiasm. Reason consists in constantly perceiving things as they really are.A Philosophical Dictionary Vol 04