"Depend upon it there comes a time when for every addition of knowledge you forget something that you knew before. It is of the highest importance, therefore, not to have useless facts elbowing out the useful ones"
About this Quote
The intent is practical and slightly teasing: don't confuse accumulation with mastery. Coming from the creator of Sherlock Holmes, the subtext clicks into place. Holmes's brilliance is famously selective; he discards trivia that doesn't help him solve the case, even bragging about not knowing that the Earth goes around the sun. Doyle isn't endorsing ignorance so much as spotlighting attention as the real scarce resource. What you keep in your head determines what patterns you can see under pressure.
Context sharpens the edge. Late-19th-century Britain was an era of expanding professionalization and swelling print culture, where "facts" were a status symbol and education could become a parlor sport. Doyle, trained as a physician and writing detective fiction that prizes inference over recitation, is pushing back against the fetish of encyclopedic knowing. "Elbowing out" is the perfect verb: useless facts aren't neutral; they're aggressive. The warning isn't anti-intellectual. It's an argument for mental curation, for building a mind that can act, not just store.
Quote Details
| Topic | Knowledge |
|---|---|
| Source | Help us find the source |
| Cite |
Citation Formats
APA Style (7th ed.)
Doyle, Arthur Conan. (2026, January 18). Depend upon it there comes a time when for every addition of knowledge you forget something that you knew before. It is of the highest importance, therefore, not to have useless facts elbowing out the useful ones. FixQuotes. https://fixquotes.com/quotes/depend-upon-it-there-comes-a-time-when-for-every-7473/
Chicago Style
Doyle, Arthur Conan. "Depend upon it there comes a time when for every addition of knowledge you forget something that you knew before. It is of the highest importance, therefore, not to have useless facts elbowing out the useful ones." FixQuotes. January 18, 2026. https://fixquotes.com/quotes/depend-upon-it-there-comes-a-time-when-for-every-7473/.
MLA Style (9th ed.)
"Depend upon it there comes a time when for every addition of knowledge you forget something that you knew before. It is of the highest importance, therefore, not to have useless facts elbowing out the useful ones." FixQuotes, 18 Jan. 2026, https://fixquotes.com/quotes/depend-upon-it-there-comes-a-time-when-for-every-7473/. Accessed 12 Feb. 2026.












