This classic, finally properly sourced, thanks to Wikiquote


All models are wrong. Some are useful.

Sometimes seen as:


All models are false but some models are useful.

Wikiquote continues: ‘The remark has two phrasings, both of which appear in George E.P. Box & Norman R. Draper, Empirical Model-Building and Response Surfaces (Wiley 1987) pp. 74 and 424: “Remember that all models are wrong; the practical question is how wrong do they have to be to not be useful.”; “Essentially, all models are wrong, but some are useful.’