The four most dangerous words in investing are: "this time it’s different."

John Templeton (1912–2008), a pioneering global value investor and founder of the Templeton Growth Fund, became known for warning against market euphoria and the belief that old valuation rules no longer apply. The line is commonly attributed to him in the context of late-stage bull markets and speculative manias, when investors justify extreme prices by claiming that new technologies, policies, or financial innovations have changed the fundamentals. Templeton’s broader investing philosophy emphasized disciplined contrarianism—buying when others are fearful and being cautious when optimism becomes unquestioning—making this aphorism a succinct summary of his skepticism toward “new era” narratives.

The quote cautions that the most perilous mistake in investing is assuming historical patterns of risk, valuation, and human behavior have been suspended. “This time it’s different” is the classic rationalization for paying too much, taking excessive leverage, or ignoring warning signs because a story (a new technology, a new monetary regime, a new metric) seems to invalidate past experience. Templeton’s point is not that change never occurs, but that investors routinely overestimate how much change eliminates cycles of greed and fear. The phrase functions as a check on narrative-driven investing: demand evidence, respect base rates, and treat extraordinary claims as a signal to re-examine risk.

1) “The four most dangerous words in the English language are: ‘This time it’s different.’”
2) “The most dangerous words in investing are, ‘This time it’s different.’”
3) “The four most dangerous words in investing: ‘This time is different.’”