If the freedom of religion, guaranteed to us by law in theory, can ever rise in practice under the overbearing inquisition of public opinion, [then and only then will truth]prevail over fanaticism.
— Thomas Jefferson
Most Powerful Religion Fanaticism quotations
There are no forces on this planet more dangerous to all of us than the fanaticisms of fundamentalism.

Muslims are the first victims of Islam.
Many times I have observed in my travels in the Orient that fanaticism comes from a small number of dangerous men who maintain the others in the practice of religion by terror. To liberate the Muslim from his religion is the best service one can render him.

In morals, what begins in fear usually ends in wickedness;
in religion, what begins in fear usually ends in fanaticism. Fear, either as a principle or a motive, is the beginning of all evil.
Time and again we see leaders and members of religions incite aggression, fanaticism, hate, and xenophobia - even inspire and legitimate violent and bloody conflicts.
There can be no fanatics in the cause of genuine liberty.
Fanaticism is excessive zeal. There may be, and have been fanatics in false religion; in the bloody religions of the heathen.

Religion without philosophy is sentiment, or sometimes fanaticism, while philosophy without religion is mental speculation.
Theological religion is the source of all imaginable follies and disturbances.
It is the parent of fanaticism and civil discord; it is the enemy of mankind.
One would think that a system loaded with such gross and vulgar absurdities as Scripture religion is could never have obtained credit; yet we have seen what priestcraft and fanaticism can do, and credulity believe.

There being in the make of an English mind a certain gloom and eagerness, which carries to the sad extreme; religion to fanaticism; free-thinking to atheism; liberty to rebellion.
it is not that religion is merely useless, it is mischievous.
It is mischievous by its idle terrors; it is mischievous by its false morality; it is mischievous by its hypocrisy; by its fanaticism; by its dogmatism; by its threats; by its hopes; by its promises.
I think that there are no forces on this planet more dangerous to us all than the fanaticisms of fundamentalism, of all the species: Protestantism, Catholicism, Judaism, Islam, Hinduism, and Buddhism, as well as countless smaller infections. Is there a conflict between science and religion here? There most certainly is.

Before one can correctly understand the work of the Holy Spirit, he must first of all know the Spirit himself. A frequent source of error and fanaticism about the work of the Holy Spirit is the attempt to study and understand His work without, first of all, coming to know Him as a person.
E.P. Whipple calls fanaticism "religion caricatured," which is a full definition in a word.
'Knowledge, without common sense,' says Lee, is 'folly;
without method, it is waste; without kindness, it is fanaticism; without religion, it is death.' But with common sense, it is wisdom with method, it is power; with charity, it is beneficence; with religion, it is virtue, and life, and peace.

Pure faith in the benevolece of the Divine can also degenerate into destructive forms of religion like othodoxy, fundamentalism, sectarianism, fanaticism, black magic and witchcraft.
In morals what begins in fear usually ends in wickedness;
in religion what begins in fear usually ends in fanaticism. Fear, either as a principle or a motive, is the beginning of all evil.
Knowledge, without common sense, says Lee, is folly;
without method, it is waste; without kindness, it is fanaticism; without religion, it is death. But with common sense, it is wisdom with method, it is power; with clarity, it is beneficence; with religion, it is virtue, and life, and peace.

All fanaticism is false, because it is a contradiction of the very nature of God and of Truth. Truth cannot be shut up in a single book, Bible or Veda or Koran, or in a single religion. The Divine Being is eternal and universal and infinite and cannot be the sole property of the Mussulmans or of the Semitic religions only, - those that happened to be in a line from the Bible and to have Jewish or Arabian prophets for their founders.
Fanaticism exists in every religion, whether Christian, Jewish, or Muslim.
Fanaticism in religion is the alliance of the passions she condemns with the dogmas she professes.

Fanaticism is a monster that pretends to be the child of religion
Fanaticism is the greatest threat today.
Literally, the 21st century threatened by fanatics, and we have fanatics in every religion, unfortunately, and what can we do against them? Words nothing else, I'm against violence but only words.
The Fanaticism which discards the Scripture, under the pretense of resorting to immediate revelations is subversive of every principle of Christianity. For when they boast extravagantly of the Spirit, the tendency is always to bury the Word of God so they may make room for their own falsehoods.

Philosophy is as far separated from impiety as religion is from fanaticism.
Everybody knows that fanaticism is religion caricatured;
bears, indeed, about the same relation to it that a monkey bears to a man; yet, with many, contempt of fanaticism is received as a sure sign of hostility to religion.
I don't think the 9/11 attacks taught us anything we didn't already know about religion. It has long been obvious - even to the deeply religious - that religious fanaticism is an extremely dangerous deranger of otherwise sane and goodhearted people.

Fanaticism is not a state of religion but a state of mind.
It is thus religion infatuates man from his infancy, fills him with vanity and fanaticism: if he has a heated imagination it drives him on to fury; if he has activity, it makes him a madman, who is frequently as cruel to himself, as he is dangerous and incommodious to others: if, on the contrary, he be phlegmatic or of a slothful habit, he becomes melancholy and is useless to society.
I had no idea, however, that in Pennsylvania, the cradle of toleration and freedom of religion, it [fanaticism] could have arisen to the height you describe. This must be owing to the growth of Presbyterianism. The blasphemy of the five points of Calvin, and the impossibility of defending them, render their advocates impatient of reasoning, irritable, and prone to denunciation.