The wit of the wise beats any number of sermons

Speaking at an Oldie literary lunch back in the day, Willie Rushton, a co-founder of Private Eye, opened his remarks with a rhetorical question: "Where would we be without a sense of humour?" He paused briefly, before delivering his answer: "Germany!"

This anecdote appears early in Quips and Quotes, Richard Ingrams's engaging anthology of sayings and anecdotes accumulated during his long career. Rushton's joke prompts me to ask a rhetorical question of my own: Where would we be without aphorisms, the short, sharp, funny, philosophical sayings of the kind so expertly collected in Ingrams's book?

In this age of austerity, where would we be without Robert Frost's, "A bank is a place where they lend you an umbrella in fair weather and ask for it back when it begins to rain"? In this post-party conference, pre-US presidential election period of political posturing, where would we be without the Polish dissident Stanislaw Lec's "Politics: a Trojan Horse race"? In this era of Keeping Up with the Kardashians, where would we be without Jean Cocteau's "Mirrors would do well to reflect a little more before sending back images"? And in this steady state of economic uncertainty, where would be we without Winston Churchill's "When you're going through hell, keep going"?

We would, I fear, be in a world without wit, a place even less humorous than Germany, for it is wit that makes these sayings so appealing – and such essential reading.

By wit, I don't just mean Groucho Marx wit, delightful as it is, which upends conventional logic in a virtuoso verbal display: "Outside of a dog, a book is man's best friend; inside of a dog, it's too dark to read." Nor do I mean Dorothy Parker's puckish wit, which deploys puns to great sardonic effect. When asked to use the word horticulture in a sentence, she replied, "You can lead a horticulture, but you can't make her think."

I mean wit in its original sense – a kind of intelligence that is clever, wise, provocative, improvised and often, though not always, funny. The relationship between wit and intelligence is still evident in the ways we use the word today. The words "outwit", "quick-witted", "dimwit", "witless", "unwitting" and even "witness" all suggest the link between wit and knowing. The connection can be traced back several thousand years through the word's etymology. Wit is related to the Sanskrit term veda, meaning knowledge, and stems from witan, an Old English word meaning to understand or to be wise.

When we hear the observation of the Russian silent film star Faina Ranevskaya: "Baldness is the gradual transformation of the head into an ass, first in shape and then in content", we laugh, yes, but we also understand something that makes us better prepared to deal with the asses we will undoubtedly encounter in our own lives.

"It is reassuring to have our half-formed views confirmed by finer minds," as Ingrams puts it, "but, more importantly, to be given tips on how to survive, not in the form of a lengthy sermon but in one or two short sentences." A collection of aphorisms is a kind of survival guide that helps us keep our wits about us even when everyone else seems to be losing theirs.

Ingrams calls his collection "a journalist's commonplace book", which he started keeping in 1958 at the suggestion of Paul Foot. The best commonplace books contain lots of common sense – practical wit that helps you get things done in the real world. I've been compiling mine since I was eight. One notable entry concerns my Uncle Jack, whose fondness for drink had transformed his nose into a topographic map of the moon and whose chain-smoking added a congested gurgle to his natural bass-baritone. As a kid, I regularly crept under the couch to tape record my parents' parties. Uncle Jack's voice always rose loud and clear above the din, a booming, buzzing infusion of reckless opinions and wildly off-key Irish folk tunes.

When Uncle Jack died, my father stood at the door of the funeral parlor, greeting people as they came to pay their last respects. Some of my cousins lingered awkwardly in the hall, unsure what to say or do. My dad chatted with them for a minute and then said, "Well, hurry up and get in there if you want to see Uncle Jack with his mouth shut." Warm wit like this makes people feel at ease and is a rare gift, indeed.

Of course, wit can also wound. In fact, many of the terms we commonly use to describe wit come from fencing. A sharp tongue is a rapier wit. A wit's unfunny sidekick is his foil. A witty verbal attack is a sally, which we parry with a riposte. Even the word touch – as in "That was a nice touch" – is drawn from the vocabulary of fencing. A "touch" is a hit with the blade that scores a point. Its source is the French word touché, an acknowledgement of a superior argument or an especially cutting remark.

In fencing, hits can only be scored by a touch with the tip of the blade; hits with the flat of the blade are ignored. The same is true of wit; witticisms are surgical strikes.

The American author Ambrose Bierce was a master of witty precision, once demolishing a rival's work in a review that read in its entirety: "The covers of this book are too far apart." Bierce's Devil's Dictionary is a curmudgeonly, commonplace book of his own misanthropic definitions: "corporation: an ingenious device for obtaining individual profit without individual responsibility"; "misfortune: the kind of fortune that never misses"; and "alone: in bad company".

No one wielded the weapon of wit better than the dastardly François, Duc de la Rochefoucauld. This 17th-century French aristocrat specialised in the darker aphoristic arts, mercilessly dissecting the more unsavoury precincts of the human heart: "Old people are fond of giving good advice; it consoles them for no longer being able to set a bad example." "The desire of the man is for the woman, but the desire of the woman is for the desire of the man." And "In the adversity of even our best friends, we always find something not wholly displeasing."

Yet even the duke cushioned his blows with black humour: "How comes it that our memories are good enough to retain even the minutest details of what has befallen us, but not to recollect how many times we have recounted them to the same person?"

Aphorisms are like vaccines: they inject a little attenuated poison into your system that boosts your resistance to the real thing. Wit gives you a shot in the arm. It smarts, but it also makes you smarter.

The French philosopher Denis Diderot invented a term for those witless instants when we don't know what to do or say – l'esprit d'escalier, which translates roughly as the wit of the staircase. We experience this whenever we think of a clever comeback only after it is too late to deliver it.

Diderot devised the phrase after being insulted at a dinner party. He was so taken aback that he thought of a suitable retort only while walking down the stairs on his way home. "A sensitive man, such as myself," he wrote, "overwhelmed by the argument levelled against him, becomes confused and can only think clearly again [when he reaches] the bottom of the stairs." Aphorisms ensure that when all else seems lost – our money, our hopes, our courage, even our very words – our wit isn't.

James Geary is the author of 'I Is an Other: The Secret Life of Metaphor' and two books about aphorisms