“It is the nature of men, having escaped one extreme, which by force they were constrained long to endure, to run headlong into the other extreme, forgetting that virtue doth always consist in the mean.”

Diary (21 December 1843), referring to Aristotle's Ethics
Diary and Letters of Rutherford Birchard Hayes (1922 - 1926)

Les femmes sont extrêmes: elles sont meilleures ou pires que les hommes.
Aphorism 53
Les Caractères (1688), Des Femmes

Source: The Limits of State Action (1792), Ch. 8
Context: Setting aside the fact that coercion and guidance can never succeed in producing virtue, they manifestly tend to weaken power; and what are tranquil order and outward morality without true moral strength and virtue? Moreover, however great an evil immorality may be, we must not forget that it is not without its beneficial consequences. It is only through extremes that men can arrive at the middle path of wisdom and virtue.

Source: Wolf Hall

The Rebel (1951)

Book of Taliesin (c. 1275?), The Pleasant Things of Taliesin
Context: A pleasant virtue, extreme penance to an extreme course;
Also pleasant, when God is delivering me.
Pleasant, the carousal that hinders not mental exertion;
Also pleasant, to drink together about horns.

1960s, Letter from a Birmingham Jail (1963)
Context: But though I was initially disappointed at being categorized as an extremist, as I continued to think about the matter I gradually gained a measure of satisfaction from the label. Was not Jesus an extremist for love: "Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you, and persecute you." Was not Amos an extremist for justice: "Let justice roll down like waters and righteousness like an ever flowing stream." Was not Paul an extremist for the Christian gospel: "I bear in my body the marks of the Lord Jesus." Was not Martin Luther an extremist: "Here I stand; I cannot do otherwise, so help me God." And John Bunyan: "I will stay in jail to the end of my days before I make a butchery of my conscience." And Abraham Lincoln: "This nation cannot survive half slave and half free." And Thomas Jefferson: "We hold these truths to be self evident, that all men are created equal..." So the question is not whether we will be extremists, but what kind of extremists we will be. Will we be extremists for hate or for love? Will we be extremists for the preservation of injustice or for the extension of justice? In that dramatic scene on Calvary's hill three men were crucified. We must never forget that all three were crucified for the same crime — the crime of extremism. Two were extremists for immorality, and thus fell below their environment. The other, Jesus Christ, was an extremist for love, truth and goodness, and thereby rose above his environment. Perhaps the South, the nation and the world are in dire need of creative extremists.

The Virtue of Selfishness (1964)

As quoted in "Age of unreason" by Jeannette Baxter in The Guardian (22 June 2004) http://www.guardian.co.uk/books/2004/jun/22/sciencefictionfantasyandhorror.jgballard
Context: The notions about the benefits of transgression in my last three novels are not ones I want to see fulfilled. Rather, they are extreme possibilities that may be forced into reality by the suffocating pressures of the conformist world we inhabit. Boredom and a deadening sense of total pointlessness seem to drive a lot of meaningless crimes, from the Hungerford and Columbine shootings to the Dando murder, and there have been dozens of similar crimes in the US and elsewhere over the past 30 years.
These meaningless crimes are much more difficult to explain than the 9/11 attacks, and say far more about the troubled state of the western psyche. My novels offer an extreme hypothesis which future events may disprove — or confirm. They're in the nature of long-range weather forecasts.