From George Bernard Shaw's review of GKC"s book A Short History of England (the review being printed in The Observer, November 4, 1917):

For Mr. Chesterton knows his epochs, and can tell you when the temple became a den of thieves, though he leaves out half the kings and gives never a date at all. Far from being discursive, as the critics are saying, he is at once the most concise and the fullest historian this distressful country has yet found.

[found in G.K. Chesterton: The Critical Judgments, Part I: 1900-1937 ed. by Denis Conlon, p. 352]

A religion should not only be instinctively absorbent of whatever is consonant with its ideal; it should also be instinctively resistant to anything that is against that ideal. Men look to a faith to purge them of all native poisons, as well as to develop all native functions and pleasures. A church should have drainage as well as ventilation. It should drive bad smells out as well as let good smells in; it should not only cast out devils, but keep them out.

-March 19, 1910, Daily News

[...] truth exists whether we like it or not, and [...] it is for us to accommodate ourselves to it.

-Chesterton on Shakespeare (1971)

Anti-clericalism is a healthy Catholic habit, spoilt by the Reformation.

-October 22, 1909, Daily News

[This quote, written while GKC was still an Anglican, is one that struck me when I first read it, but one I'm coming to understand better these days, unfortunately.] 

"The high tide!" King Alfred cried.
"The high tide and the turn!
As a tide turns on the tall grey seas,
See how they waver in the trees,
How stray their spears, how knock their knees,
How wild their watchfires burn!

-The Ballad of the White Horse (1911)

It isn't that they can't see the solution. It is that they can't see the problem.

-The Scandal of Father Brown (1935)

And the fact which has created (I am sorry to say) a general impression that [they...] are a pack of shuffling humbugs, is exactly the fact that they do [...] give way to merely instinctive tastes and passions at the expense of the first principle which they are supposed to hold [...] They will upset their whole philosophy to upset one person whom they dislike [...] And they think that they can give to reform all its original energy merely because when they see something that they very much want to do, they do it with a great deal of gusto. But the old acts of justice were not most powerful when they were performed with gusto. Rather they were more powerful when they were performed with reluctance. Men thought more of the strength of the creed when they saw the creed compelling the man [...] Political consistency of this kind people felt had something of the naked dignity of the great dogmatic religions which it seemed to ignore. A political faith ought to have, like a religious faith, a slight element of mortification: it ought either to mortify the flesh or, what is (in the case of prigs) much more important and valuable, to mortify the spirit.

-October 12, 1907, Illustrated London News

"She hasn't got any intellect to speak of; but you don't need any intellect to be an intellectual."

-The Scandal of Father Brown (1935)

Democracy is never quite democratic except when it is quite direct; and it is never quite direct except when it is quite small. So soon as a mob has grown large enough to have delegates it has grown large enough to have despots; indeed the despots are often much the more representative of the two.

-The New Jerusalem (1920)

But any man of moral experience will know that there is no pride so wholesome as the pride in something that does him no credit. That is why love is the parent of the highest pride, because it is pride in a happiness which cannot be anything but undeserved. Similarly it cannot fail to be elevating to a man to boast of great battles that he never saw, and to plume himself with a certain agreeable vanity upon splendid actions that he did not perform. In this kind of exaltation a man is proud at the same moment that he is humble. He feels the profound philosophic truth that his own greatest merits are as much dependent upon nature as the merits of his remotest ancestors. to him his own most dazzling impromptu is as much a gift as the grass in the meadow. He will not therefore resent being called upon to exult in the wonders of other ages or the deeds of other men. No one can have failed to notice that the only kind of conceit which is really vulgar and pitiful is the conceit of the man who has himself something of which to be conceited.

-July 10, 1901, Daily News

"A taste for low company doesn't make people thieves," said Murrel, "it's generally a taste for high company that does that."

-The Return of Don Quixote (1927)

A poet may be vague, and a mystic hates vagueness. A poet is a man who mixes up heaven and earth unconsciously. A mystic is a man who separates heaven and earth even if he enjoys them both.

-William Blake (1910)

From an interview with Fr. Paul Scalia (the son of the late Supreme Court Justice Antonin Scalia):

Q: What writers influence you and why?

A: Probably the writer who has influenced me the most is G.K. Chesterton because he can turn a phrase. His writing is fun. Ronald Knox, his writing is excellent. I think with both of them there is both a down-to-earthness about them. There is a levity and there is a precision.

"Fr. Paul Scalia Talks New Book"

[...] the fundamental things in a man are not the things he explains, but rather the things he forgets to explain.

-The Superstition of Divorce (1920)

A dream can commonly be described as possessing an utter discordance of incident combined with a curious unity of mood; everything changes but the dreamer. It may begin with anything and end with anything, but if the dreamer is sad at the end he will be sad as if by prescience at the beginning; if he is cheerful at the beginning he will be cheerful if the stars fail. A Midsummer Night's Dream has in a most singular degree effected this difficult, this almost desperate subtlety. The events in the wandering wood are in themselves, and regarded as in broad daylight, not merely melancholy but bitterly cruel and ignominious. But yet by the spreading of an atmosphere as magic as the fog of Puck, Shakespeare contrives to make the whole matter mysteriously hilarious while it is palpably tragic, and mysteriously charitable, while it is in itself cynical [...] The creation of a brooding sentiment like this, a sentiment not merely independent of but actually opposed to the events, is a much greater triumph of art than the creation of the character of Othello.

-Chesterton on Shakespeare (1971)

[..] men like Chaucer and Langland may have supported Wycliffe to some extent in practice, and then repudiated him more completely in theory, for a particular reason of their own. The reason was (odd as it will sound in modern ears) that they supported him when he was right and repudiated him when he was wrong.

Wycliffe was only one example of a man who yields to a temptation, which few reformers have been sufficiently clear-headed to resist. He became so irritated with the fact that the Idea was badly carried out in practice, that at last he was weak enough to turn and attack the Idea in theory. [...] But there is here some haunting temptation which perpetually betrays reformers. It betrays the reformers of modern as of medieval times [...] The logical, or rather illogical, process is perfectly simple and perfectly familiar. A man sets out to distribute Milk to mothers or families or the whole community. He very soon discovers that distribution is not so easy as it looks. Before long he is perfectly familiar with the fact of people intercepting milk, stealing milk, making a corner in milk, adulterating milk, poisoning milk. He is very naturally in a rage, which verges on a revolutionary rage; nor is he wrong in proposing even precipitate and violent action against those who swindle about milk or poison milk. But there always comes a time when he is tempted to turn, in a towering passion, and say, 'There shall be no Milk.' That is what happened at the Reformation. That is what happens in nearly every revolution.

-Chaucer (1932)

But civilisation is to be tested not so much by the dexterity of inventions as by the worth of what is invented. Many of the instruments of torture in the Tower of London display great dexterity of invention. Civilisation is not to be judged by the rapidity of communication, but by the value of what is communicated. I can send to my next-door neighbour the message- "You are an ass." I have not greatly advanced in civilisation merely because I can send the same intelligent message to a man in Australia.

-February 16, 1907, Illustrated London News

Our need for rules does not arise from the smallness of our intellects, but from the greatness of our task. Discipline is not necessary for things that are slow and safe; but discipline is necessary for things that are swift and dangerous. We do not need a map for a stroll; but we do need a map for a raid. Now Western democracy is certainly engaged in a raid, a raid on the New Jerusalem. We are trying to do right: one of the wildest perils. We are trying to bring political equity on earth; to materialise an almost incredible justice [...] The thing has nothing to do with the freedom of the mind. Cervantes at Lepanto would have obeyed orders; surely not because he wore blinkers, but because Cervantes knew that there are twenty ways of criticising a battle, but only one way of winning it. And I do not believe for a moment that the ordinary man only obeys social rules because he is too stupid to see the alternative; I believe he obeys them because he feels, though he cannot perhaps express the fact, that they are the only way of having a rapid and reasonable human activity.

-September 28, 1907, Daily News

Pride consists in a man making his personality the only test, instead of making the truth the test.  It is not pride to wish to do well, or even to look well, according to a real test.  It is pride to think that a thing looks ill, because it does not look like something characteristic of oneself.  Now in the general clouding of clear and abstract standards, there is a real tendency today for a young man (and even possibly a young woman) to fall back on that personal test, simply for lack of any trustworthy impersonal test.  No standard being sufficiently secure for the self to be moulded to suit it, all standards may be moulded to suit the self.  But the self as a self is a very small thing and something very like an accident.  Hence arises a new kind of narrowness; which exists especially in those who boast of breadth.  The sceptic feels himself too large to measure life by the largest things; and ends by measuring it by the smallest thing of all. 

-The Common Man (1950)

"...ambition narrows as the mind expands."

But youth is always ambitious and universal; mature work exhibits more of individuality, more of the special type and colour of work which a man is destined to do. Youth is universal, but not individual. The genius who begins life with a very genuine and sincere doubt whether he is meant to be an exquisite and idolised violinist, or the most powerful and eloquent Prime Minister of modern times, does at last end by making the discovery that there is, after all, one thing, possibly a certain style of illustrating Nursery Rhymes, which he can really do better than any one else. This was what happened to Browning; like every one else, he had to discover first the universe, and then humanity, and at last himself. With him, as with all others, the great paradox and the great definition of life was this, that the ambition narrows as the mind expands.

-Robert Browning (1903)

We are all somewhat wearily aware that some Modern Churchman call such continuous change progress;  as when we remark that a corpse crawling with worms has an increased vitality; or that a snow-man, slowly turning into a puddle, is purifying itself of its accretions.

-The Well and the Shallows (1935)

"What do you think about spirits?"

"Never touch 'em," said the Colonel. "Sound port never hurt anybody."

"I mean the other sort," said Pierce. "Things like ghosts and all that."

"I don't know," said Owen Hood. "The Greek for it is agnosticism. The Latin for it is ignorance. But have you really been dealing with ghosts and spirits down at poor White's parsonage?"

"I don't know," said Pierce gravely.

"You don't mean you really think you saw something!" cried Hood sharply.

"There goes the agnostic!" said Pierce with a rather weary smile. "The minute the agnostic hears a bit of real agnosticism he shrieks out that it's superstition."

-Tales of the Long Bow (1925)

But do not be kind merely to exhibit your own kindness; for that is an insult that is never forgiven. When you are helping people, pray for a spirit of humility; I had almost said, when you are helping people, pray for an appearance of helplessness.

-Sidelights (1932)

An interesting article on Distributism, the (admittedly awkward and to an extent misleading) name of the economic philosophy of Chesterton.

"There are some proposals and propositions in which a middle course is a great deal more insane than either extreme ..."

The English, however, along with their admirable virtues have one very impracticable delusion. They tend to think that an extreme course must be unreasonable, and that a middle course must be reasonable. This, of course, depends entirely on the nature of the proposal or proposition involved. There are some proposals and propositions in which a middle course is a great deal more insane than either extreme, but even in these we tend as a nation to adopt the moonstruck compromise. If anybody suggested, let us say, that Dr. Clifford should be boiled in oil we may be quite certain that 'The Times' or 'The Daily Telegraph' would write: 'Yielding to none in our Imperial sentiment, we cannot agree with those who propose to boil the Doctor in the extreme sense of the phrase. On the other hand, no one will suspect us of any sympathy with the visionaries who suggest the fantastic course of not boiling him at all. The English are a shrewd and practical people. They will not be seduced by either fanaticism to desert the sensible and medium course they have adopted, that of boiling Dr. Clifford's feet for twenty-five minutes. If the followers of that gentleman will not accept this fair and generous concession, they must be altogether unfit for the give-and-take of practical politics'. That is how the English really argue in a great many matters. But there have been from time to time men among us who have felt that this worship of compromise as compromise was not sensible in the least. They have felt that a position was not necessarily unreasonable merely because it was consistent and clear. They have felt that a position was not necessarily reasonable merely because it was neither fish, flesh, or herring. They held that if a sane man had views at all, it was a part of his sanity to see the views fully and to see far into them. In short, they regarded the thing called 'moderation' as one of the cloudiest manias of the asylum.

-August 1, 1903, Daily News

There is a great deal of difference between the optimism which says that things are perfect and the optimism which merely says (with a more primeval modesty) that they are very good. One optimism says that a one-legged man has two legs because it would be so dreadful if he had not. The other optimism says that the fact that the one-legged was born of a woman, has a soul, has been in love, and has stood alive under the stars, is a fact so enormous and thrilling that, in comparison, it does not matter whether he has one leg or five. One optimism says that this is the best of all possible worlds. The other says that it is certainly not the best of all possible worlds, but it is the best of all possible things that a world should be possible.

-G.F. Watts (1904)

It is a good sign in a nation when such things are done badly. It shows that all the people are doing them. And it is a bad sign in a nation when such things are done very well, for it shows that only a few experts and eccentrics are doing them, and that the nation is merely looking on. Suppose that whenever we heard of walking in England it always meant walking forty-five miles a day without fatigue. We should be perfectly certain that only a few men were walking at all, and that all the other British subjects were being wheeled about in Bath-chairs. But if when we hear of walking it means slow walking, painful walking, and frequent fatigue, then we know that the mass of the nation still is walking. We know that England is still literally on its feet.

-All Things Considered (1908)

All modern thinkers are reactionaries; for their thought is always a reaction from what went before.

-What's Wrong With the World (1910)

The modern world has many marks, good as well as bad; but by far the most modern thing in it is the abandonment of individual reason, in favour of press stunts and suggestion and mass psychology and mass production.

-The Thing (1929)

The only thing which we can safely prophesy is the one thing which is always called impossible. Again and again we are told, by all sorts of priggish and progressive persons, that mankind cannot go back. The answer is that if mankind cannot go back, it cannot go anywhere. Every important change in history has been founded on something historic: and if the world had not again and again tried to renew its youth, it would have been dead long ago.

-Robert Louis Stevenson (1927)

Rosetti makes the remark somewhere, bitterly but with great truth, that the worst moment for the atheist is when he is really thankful and has nobody to thank. The converse of this proposition is also true; and it is certain that this gratitude produced, in such men as we are here considering, the most joyful moments that have been known to man. The great painter boasted that he mixed all his colors with brains, and the great saint may be said to mix all his thoughts with thanks.

-St. Francis of Assisi (1923)