It is wrong to think that the task of physics is to find out how Nature is. Physics concerns what we say about Nature.

This remark is associated with Bohr’s mature reflections on quantum mechanics, especially the “Copenhagen” emphasis on complementarity and the limits of classical description. In debates of the 1920s–1950s about what quantum theory says the world is “really like” (including exchanges with Einstein and later discussions with philosophers and physicists), Bohr repeatedly stressed that physics is an enterprise of formulating communicable statements about experimental arrangements and outcomes. The quote encapsulates his resistance to naïve realism: quantum phenomena cannot be cleanly separated from the conditions under which they are observed and described, so the aim of physics is not metaphysical disclosure of Nature-in-itself but precise, shared language about observations.

Bohr is expressing a core theme of the Copenhagen interpretation: physics is not a God’s-eye description of an observer-independent reality, but a disciplined way of formulating and communicating what can be said—operationally and unambiguously—about experimental outcomes. In quantum mechanics, the measuring arrangement and the language used to report results are inseparable from what is meaningfully assertable. The quote pushes back against naive realism (“how Nature is in itself”) and emphasizes epistemic humility: theories are tools for organizing experience and predicting observations, not final metaphysical portraits. It also highlights Bohr’s insistence on classical language for describing experiments, even when the underlying phenomena are quantum.

1) “It is wrong to think that the task of physics is to find out how nature is. Physics concerns what we can say about nature.”
2) “Physics is not about how the world is; it is about what we can say about the world.”