I’d never seen this quote from Richard Feynman on the measurement problem:
When you start out to measure the property of one (or more) atom, say, you get for example, a spot on a photographic plate which you then interpret. But such a spot is really only more atoms & so in looking at the spot you are again measuring the properties of atoms, only now it is more atoms. What can we expect to end with if we say we can’t see many things about one atom precisely, what in fact can we see? Proposal,
Only those properties of a single atom can be measured which can be correlated (with finite probability) (by various experimental arrangements) with an unlimited no. o f atoms.
(I.e. the photographic spot is “real” because it can be enlarged & projected on screens, or affect large vats of chemicals, or big brains, etc., etc. – it can be made to affect ever increasing sizes of things – it can determine whether a train goes from N.Y. to Chic. – or an atom bomb explodes – etc.)
This is from a set of notes dating to 1946 as detailed in Silvan S. Schweber, “Feynman and the visualization of space-time processes” Rev. Mod. Phys. 58, 449 – 508 (1986).