--- title: "Meaning & Key Takeaway of: Mark Twain said a century ago, “It’s not…" description: "\"“Mark Twain said a century ago, “It’s not what you don’t know that gets you into trouble, it’s what you know for sure that ain’t so.”\" — Tom Kelley" image: "https://sms4smile.com/quotes/i/421/tom-kelley-24374_mark-twain_mark-twain-said-a-century-ago-it-s-not-w_859982.png" --- # Mark Twain said a century ago, “It’s not what you don’t… ![“Mark Twain said a century ago, “It’s not what you don’t know that gets you into trouble, it’s what you know for sure that ain’t so.” quote by Tom Kelley](https://sms4smile.com/quotes/i/421/tom-kelley-24374_mark-twain_mark-twain-said-a-century-ago-it-s-not-w_859982.png) [Download](https://sms4smile.com/quotes/i/421/tom-kelley-24374_mark-twain_mark-twain-said-a-century-ago-it-s-not-w_859982.png) [Open image](https://sms4smile.com/quotes/i/421/tom-kelley-24374_mark-twain_mark-twain-said-a-century-ago-it-s-not-w_859982.png) > ““Mark Twain said a century ago, “It’s not what you don’t know that gets you into trouble, it’s what you know for sure that ain’t so.”” [Tom Kelley](https://sms4smile.com/quotes/author/tom-kelley/) ## About This Quote This interpretation was drafted with AI assistance. It is one reading of the quote, not the author's own explanation. Highlights that overconfidence in known facts leads to errors, urging humility and curiosity. **In simple terms:** Overconfidence can mislead. Key Takeaway Question assumptions and stay curious. Themes humility learning critical thinking Mood thoughtful inquisitive Type philosophical advice When to use this quote - product development - education - decision making Key Concepts cognitive bias innovation knowledge management Questions to Reflect On - How can you test what you think you know? - When did overconfidence cause a mistake? A Different Perspective May overlook the value of expertise. ★ ★ ★ ★ ★ No ratings yet ## Related quotes > [“Mark Twain said “it ain’t what you don’t know that gets you into trouble, but what you know for sure that just ain’t so.”](https://sms4smile.com/quotes/terence-callery/mark-twain-said-it-ain-t-what-you-don-t-know-that-gets-you-into/) [Terence Callery](https://sms4smile.com/quotes/author/terence-callery/) > [“It’s not what you don’t know that gets you in trouble. It’s what you do know that ain’t so. —Will Rogers or Mark Twain…](https://sms4smile.com/quotes/edward-b-burger/it-s-not-what-you-don-t-know-that-gets-you-in-trouble-it-s-what-you/) [Edward B. Burger](https://sms4smile.com/quotes/author/edward-b-burger/) > [“Mark Twain said that Adam was the only man who, when he said a good thing, knew that nobody had said it before.”](https://sms4smile.com/quotes/anne-lamott/mark-twain-said-that-adam-was-the-only-man-who-when-he-said-a-good/) [Anne Lamott](https://sms4smile.com/quotes/author/anne-lamott/) > [“Ben smiled back, 'Mark Twain said a novel was a confession to everything by a man who had never done anything.”](https://sms4smile.com/quotes/stephen-king/ben-smiled-back-mark-twain-said-a-novel-was-a-confession-to/) [Stephen King](https://sms4smile.com/quotes/author/stephen-king/) > [“Mark Twain once said, “I can live for two months on a good compliment.”](https://sms4smile.com/quotes/gary-chapman/mark-twain-once-said-i-can-live-for-two-months-on-a-good-compliment/) [Gary Chapman](https://sms4smile.com/quotes/author/gary-chapman/) > [I think it was Mark Twain who said, “Get your facts straight, and then you can distort them as much as you like.](https://sms4smile.com/quotes/josh-lanyon/i-think-it-was-mark-twain-who-said-get-your-facts-straight-and-then/) [Josh Lanyon](https://sms4smile.com/quotes/author/josh-lanyon/) > [To make fun of an administration, to make fun of anything, Mark Twain said, is the last defense of democracy.](https://sms4smile.com/quotes/robin-williams/to-make-fun-of-an-administration-to-make-fun-of-anything-mark-twain/) [Robin Williams](https://sms4smile.com/quotes/author/robin-williams/) > [“History may not repeat itself but, as Mark Twain said, it does rhyme.”](https://sms4smile.com/quotes/paul-kriwaczek/history-may-not-repeat-itself-but-as-mark-twain-said-it-does-rhyme/) [Paul Kriwaczek](https://sms4smile.com/quotes/author/paul-kriwaczek/) > [Those who have heard me speak from time to time know that quite often I cite the observation of that great American author, Mark…](https://sms4smile.com/quotes/j-d-hayworth/those-who-have-heard-me-speak-from-time-to-time-know-that-quite-often/) [J. D. Hayworth](https://sms4smile.com/quotes/author/j-d-hayworth/) > [“Mark Twain said, two people can keep a secret if one of them is dead.”](https://sms4smile.com/quotes/kaje-harper/mark-twain-said-two-people-can-keep-a-secret-if-one-of-them-is-dead/) [Kaje Harper](https://sms4smile.com/quotes/author/kaje-harper/) > [Mark Twain once said that history doesn't repeat itself, but it does rhyme.](https://sms4smile.com/quotes/albert-laszlo-barabasi/mark-twain-once-said-that-history-doesn-t-repeat-itself-but-it-does/) Albert-Laszlo Barabasi > [“Mark Twain said, "Humor is mankind's greatest blessing." Dorsey Bing said, "I'll take womankind's greatest blessing: more wine.”](https://sms4smile.com/quotes/cece-osgood/mark-twain-said-humor-is-mankind-s-greatest-blessing-dorsey-bing-said/) CeCe Osgood > [“We are so identified with who we think we are that it limits how we can be, determines how we live, and conditions how…](https://sms4smile.com/quotes/lama-surya-das/we-are-so-identified-with-who-we-think-we-are-that-it-limits-how-we/) [Lama Surya Das](https://sms4smile.com/quotes/author/lama-surya-das/) > [“Mark Twain said that, outside of Vienna, all coffee was merely liquid poverty," Sarah commented.”](https://sms4smile.com/quotes/magnus-flyte/mark-twain-said-that-outside-of-vienna-all-coffee-was-merely-liquid/) [Magnus Flyte](https://sms4smile.com/quotes/author/magnus-flyte/) > [“LEARN FROM THE MASTERS: Mark Twain once said, “Show, don’t tell.” This is an incredibly important lesson for writers to remember; never get such…](https://sms4smile.com/quotes/colin-nissan/learn-from-the-masters-mark-twain-once-said-show-don-t-tell-this-is/) [Colin Nissan](https://sms4smile.com/quotes/author/colin-nissan/) ## More by Tom Kelley > [The head that once was crowned with thorns Is crowned with glory now.](https://sms4smile.com/quotes/tom-kelley/the-head-that-once-was-crowned-with-thorns-is-crowned-with-glory-now/) [Tom Kelley](https://sms4smile.com/quotes/author/tom-kelley/) > [If simplicity were easy, we would see more of it.](https://sms4smile.com/quotes/tom-kelley/if-simplicity-were-easy-we-would-see-more-of-it/) [Tom Kelley](https://sms4smile.com/quotes/author/tom-kelley/) > [“Great groups ship. “They are places of action, not think tanks or retreat centers devoted solely to the generation of ideas.” Warren characterized the…](https://sms4smile.com/quotes/tom-kelley/great-groups-ship-they-are-places-of-action-not-think-tanks-or/) [Tom Kelley](https://sms4smile.com/quotes/author/tom-kelley/) > [If you want a team of smart, creative people to do extraordinary things, don't put them in a drab, ordinary space.](https://sms4smile.com/quotes/tom-kelley/if-you-want-a-team-of-smart-creative-people-to-do-extraordinary/) [Tom Kelley](https://sms4smile.com/quotes/author/tom-kelley/) > [“No matter how high you rise in your career, no matter how much expertise you gain, you still need to keep your knowledge and…](https://sms4smile.com/quotes/tom-kelley/no-matter-how-high-you-rise-in-your-career-no-matter-how-much/) [Tom Kelley](https://sms4smile.com/quotes/author/tom-kelley/) > [Fail early, fail often, in order to succeed sooner.](https://sms4smile.com/quotes/tom-kelley/fail-early-fail-often-in-order-to-succeed-sooner/) [Tom Kelley](https://sms4smile.com/quotes/author/tom-kelley/) > [“New opportunities for innovation open up when you start the creative problem-solving process with empathy toward your target audience—whether”](https://sms4smile.com/quotes/tom-kelley/new-opportunities-for-innovation-open-up-when-you-start-the-creative/) [Tom Kelley](https://sms4smile.com/quotes/author/tom-kelley/) > [“But as you look at the sweep of your life and start to think of a legacy that survives beyond it, giving others the…](https://sms4smile.com/quotes/tom-kelley/but-as-you-look-at-the-sweep-of-your-life-and-start-to-think-of-a/) [Tom Kelley](https://sms4smile.com/quotes/author/tom-kelley/) > [“I used to think that to make something happen in a corporation or in the army, you had to be at the higher ranks,…](https://sms4smile.com/quotes/tom-kelley/i-used-to-think-that-to-make-something-happen-in-a-corporation-or-in/) [Tom Kelley](https://sms4smile.com/quotes/author/tom-kelley/) > [“But to act, most of us must first overcome the fears that have blocked our creativity in the past.”](https://sms4smile.com/quotes/tom-kelley/but-to-act-most-of-us-must-first-overcome-the-fears-that-have-blocked/) [Tom Kelley](https://sms4smile.com/quotes/author/tom-kelley/) > [“Work doesn’t have to feel like “Work with a capital W.” You should be able to feel passion, purpose, and meaning in whatever you…](https://sms4smile.com/quotes/tom-kelley/work-doesn-t-have-to-feel-like-work-with-a-capital-w-you-should-be/) [Tom Kelley](https://sms4smile.com/quotes/author/tom-kelley/) > [“Great groups believe they are on a mission from God. Beyond mere financial success, they genuinely believe they will make the world a better…](https://sms4smile.com/quotes/tom-kelley/great-groups-believe-they-are-on-a-mission-from-god-beyond-mere/) [Tom Kelley](https://sms4smile.com/quotes/author/tom-kelley/) > [“So design your space for flexibility instead of inertia and the status quo.”](https://sms4smile.com/quotes/tom-kelley/so-design-your-space-for-flexibility-instead-of-inertia-and-the/) [Tom Kelley](https://sms4smile.com/quotes/author/tom-kelley/) > [“Friedrich Nietzsche said, “All truly great thoughts are conceived by walking.”](https://sms4smile.com/quotes/tom-kelley/friedrich-nietzsche-said-all-truly-great-thoughts-are-conceived-by/) [Tom Kelley](https://sms4smile.com/quotes/author/tom-kelley/) > [I'm not gonna be perfect, but I'm gonna try stuff.](https://sms4smile.com/quotes/tom-kelley/i-m-not-gonna-be-perfect-but-i-m-gonna-try-stuff/) [Tom Kelley](https://sms4smile.com/quotes/author/tom-kelley/) [Explore all 24 Tom Kelley quotes ](https://sms4smile.com/quotes/author/tom-kelley/) ## More Mark twain quotes > [“China reminds me most of America at its own moment of transformation—the period that Mark Twain and Charles Warner named the Gilded Age, when…](https://sms4smile.com/quotes/evan-osnos/china-reminds-me-most-of-america-at-its-own-moment-of-transformation/) [Evan Osnos](https://sms4smile.com/quotes/author/evan-osnos/) > [“I told him that if we doubted that we are demons in Hell, he should read The Mysterious Stranger, which Mark Twain wrote in…](https://sms4smile.com/quotes/kurt-vonnegut/i-told-him-that-if-we-doubted-that-we-are-demons-in-hell-he-should/) [Kurt Vonnegut](https://sms4smile.com/quotes/author/kurt-vonnegut/) > [As a Nobel Prize winner I cannot but regret that the award was never given to Mark Twain, nor to Henry James, speaking only…](https://sms4smile.com/quotes/ernest-hemingway/as-a-nobel-prize-winner-i-cannot-but-regret-that-the-award-was-never/) [Ernest Hemingway](https://sms4smile.com/quotes/author/ernest-hemingway/) > [Where is it written that if you don't like religion you are somehow disqualified from being a legitimate American? What was Mark Twain, a…](https://sms4smile.com/quotes/hendrik-hertzberg/where-is-it-written-that-if-you-don-t-like-religion-you-are-somehow/) [Hendrik Hertzberg](https://sms4smile.com/quotes/author/hendrik-hertzberg/) > [The critique of social inequality, which is very much a part of my story, came about naturally from my recollection of Huck and Tom…](https://sms4smile.com/quotes/norman-lock/the-critique-of-social-inequality-which-is-very-much-a-part-of-my/) [Norman Lock](https://sms4smile.com/quotes/author/norman-lock/) > [Mark Twain didn't psychoanalyze Huck Finn or Tom Sawyer. Dickens didn't put Oliver Twist on the couch because he was hungry! Good copy comes…](https://sms4smile.com/quotes/samuel-fuller/mark-twain-didn-t-psychoanalyze-huck-finn-or-tom-sawyer-dickens-didn/) [Samuel Fuller](https://sms4smile.com/quotes/author/samuel-fuller/) > [To make fun of an administration, to make fun of anything, Mark Twain said, is the last defense of democracy.](https://sms4smile.com/quotes/robin-williams/to-make-fun-of-an-administration-to-make-fun-of-anything-mark-twain/) [Robin Williams](https://sms4smile.com/quotes/author/robin-williams/) > [“Never let school get in the way of your education. Mark Twain”](https://sms4smile.com/quotes/evelyn-krieger/never-let-school-get-in-the-way-of-your-education-mark-twain/) Evelyn Krieger > [Mark Twain had a way of telling stories that shifts your consciousness away from labels.](https://sms4smile.com/quotes/val-kilmer/mark-twain-had-a-way-of-telling-stories-that-shifts-your/) [Val Kilmer](https://sms4smile.com/quotes/author/val-kilmer/) > [Sing like no one's listening, love like you've never been hurt, dance like nobody's watching, and live like its heaven on earth. Â Mark Twain](https://sms4smile.com/quotes/mark-twain/sing-like-no-one-s-listening-love-like-you-ve-never-been-hurt-dance-2/) [Mark Twain](https://sms4smile.com/quotes/author/mark-twain/) > ['Don't go around saying the world owes you a living. The world owes you nothing. It was here first.' Mark Twain](https://sms4smile.com/quotes/anonymous/don-t-go-around-saying-the-world-owes-you-a-living-the-world-owes-you/) [Anonymous](https://sms4smile.com/quotes/author/anonymous/) > [“If my name were Mark Twain, I’d write under the pseudonym “Samuel Clemens.”](https://sms4smile.com/quotes/jarod-kintz/if-my-name-were-mark-twain-i-d-write-under-the-pseudonym-samuel/) [Jarod Kintz](https://sms4smile.com/quotes/author/jarod-kintz/) > [“A half-century later, Mark Twain would say that the gold rush drastically changed the American character, ending the tradition of patient apprenticeships, the gradual…](https://sms4smile.com/quotes/pete-hamill/a-half-century-later-mark-twain-would-say-that-the-gold-rush/) [Pete Hamill](https://sms4smile.com/quotes/author/pete-hamill/) > [I never dreamed I would receive the Mark Twain Prize for American Humor, mostly because my style is so typically Austrian.](https://sms4smile.com/quotes/tina-fey/i-never-dreamed-i-would-receive-the-mark-twain-prize-for-american/) [Tina Fey](https://sms4smile.com/quotes/author/tina-fey/) > [“The truth is a fragile thing, but a lie, well told, can live forever. “ — Mark Twain”](https://sms4smile.com/quotes/rebecca-nugent/the-truth-is-a-fragile-thing-but-a-lie-well-told-can-live-forever/) Rebecca Nugent Browse all 225 Mark twain quotes ```json { "@context": "https://schema.org", "@graph": [ { "@type": "Quotation", "text": "“Mark Twain said a century ago, “It’s not what you don’t know that gets you into trouble, it’s what you know for sure that ain’t so.”", "creator": { "@type": "Person", "name": "Tom Kelley" }, "isPartOf": { "@id": "https://sms4smile.com/quotes/#website" }, "url": "https://sms4smile.com/quotes/tom-kelley/mark-twain-said-a-century-ago-it-s-not-what-you-don-t-know-that-gets/", "about": { "@type": "Thing", "name": "Mark twain" }, "@id": "https://sms4smile.com/quotes/tom-kelley/mark-twain-said-a-century-ago-it-s-not-what-you-don-t-know-that-gets/#quotation", "image": { "@type": "ImageObject", "@id": "https://sms4smile.com/quotes/i/421/tom-kelley-24374_mark-twain_mark-twain-said-a-century-ago-it-s-not-w_859982.png", "contentUrl": "https://sms4smile.com/quotes/i/421/tom-kelley-24374_mark-twain_mark-twain-said-a-century-ago-it-s-not-w_859982.png", "url": "https://sms4smile.com/quotes/i/421/tom-kelley-24374_mark-twain_mark-twain-said-a-century-ago-it-s-not-w_859982.png", "width": 1080, "height": 1080, "caption": "“Mark Twain said a century ago, “It’s not what you don’t know that gets you into trouble, it’s what you know…” — Tom Kelley", "creditText": "SMS4Smile Quotes", "creator": { "@id": "https://sms4smile.com/quotes/#organization" } } }, { "@type": "BreadcrumbList", "itemListElement": [ { "@type": "ListItem", "position": 1, "name": "Home", "item": "https://sms4smile.com/" }, { "@type": "ListItem", "position": 2, "name": "Quotes", "item": "https://sms4smile.com/quotes/" }, { "@type": "ListItem", "position": 3, "name": "Tom Kelley", "item": "https://sms4smile.com/quotes/author/tom-kelley/" }, { "@type": "ListItem", "position": 4, "name": "“Mark Twain said a century ago,...", "item": "https://sms4smile.com/quotes/tom-kelley/mark-twain-said-a-century-ago-it-s-not-what-you-don-t-know-that-gets/" } ], "@id": "https://sms4smile.com/quotes/tom-kelley/mark-twain-said-a-century-ago-it-s-not-what-you-don-t-know-that-gets/#breadcrumb" }, { "@type": "WebSite", "@id": "https://sms4smile.com/quotes/#website", "name": "SMS4Smile Quotes", "url": "https://sms4smile.com/quotes/", "publisher": { "@id": "https://sms4smile.com/quotes/#organization" } }, { "@type": "Organization", "@id": "https://sms4smile.com/quotes/#organization", "name": "SMS4Smile Quotes", "url": "https://sms4smile.com/quotes/", "logo": { "@type": "ImageObject", "url": "https://sms4smile.com/quotes/wp-content/themes/sq/assets/icons/icon-512.png", "width": 512, "height": 512 } } ] } ```