„In quantum physics, however, each observation implies an intervention in the observed. Because of the quantum physical laws of nature, a change of state of the observed is inevitably coupled to the observation process. So it's not a situation independent from the experiment that is observed, but we ourselves call forth the facts (or compel them to go in a certain direction to a disambiguation), that then become an observation.“
— Pascual Jordan
Quantenmechanische Bemerkungen zur Biologie und Psychologie, Erkenntnis, Vol. 4 (1934). p. 228.