M.l. Von Franz said this quote

“ ...in microphysics the observer interferes with the experiment in a way that can't be measured and that therefore can't be eliminated. No natural laws can be formulated, saying such-and-such will happen in every case. All the microphysicist can say is such-and-such is, according to statistical probability, likely to happen. This naturally represents a tremendous problem for our classical physical thinking. It requires a consideration, in a scientific experiment, of the mental outlook of the participant-observer: It could this be said that scientists can no longer hope to describe any aspects or qualities of outer objects in a completely independent, objective manner. ”