To leave the atom constituted as it was but to interfere with the probability of its undetermined behaviour, does not seem quite so drastic an interf… - Arthur Eddington

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To leave the atom constituted as it was but to interfere with the probability of its undetermined behaviour, does not seem quite so drastic an interference with natural law as other modes of mental interference that have been suggested. (Perhaps that is only because we do not understand enough about these probabilities to realize the heinousness of our suggestion.) Unless it belies its name, probability can be modified in ways which ordinary physical entities would not admit of. There can be no unique probability attached to any event or behaviour; we can only speak of 'probability in the light of certain given information,' and the probability alters according to the extent of the information. It is, I think, one of the most unsatisfactory features of the new quantum theory in its present stage that it scarcely seems to recognize this fact, and leaves us to guess at the basis of information to which its probability theorems are supposed to refer.