# if all you have is a hammer, everything looks like a nail

> English word · Proverb

## Definitions
1. With limited tools, single-minded people apply them inappropriately or indiscriminately.
2. Individuals deeply versed in a particular subject or proficient in the use of a specific tool may display confirmation bias, viewing it as relevant to all situations.

## Etymology
Likely traditional. In this form, perhaps from Abraham Maslow, The Psychology of Science, 1966, page 15 and his earlier book
Abraham H. Maslow (1962), Toward a Psychology of Being:
: I suppose it is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail.
Similar concept by Abraham Kaplan, The Conduct of Inquiry: Methodology for Behavioral Science, 1964, page 28:
: I call it the law of the instrument, and it may be formulated as follows: Give a small boy a hammer, and he will find that everything he encounters needs pounding.
Labeled "Baruch's Observation" (after Bernard Baruch) in The Complete Murphy's Law: A Definitive Collection (1991) by Arthur Bloch.
Also often attributed, without citation, to Mark Twain (for example in Jonathan Haidt, The Righteous Mind, page 9).

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/if-all-you-have-is-a-hammer-everything-looks-like-a-nail