Being somewhat bothered by the some of the statements on quantum mechanics made on this list, a couple weeks ago I queried a physicist friend on the topic and got the following reply. Carrol ----- something better: a set of experiments that presented particle and wave properties for one thing, along with several other mounting contradictions, forced a change in the structure of physical theory. the resulting theory forced us to better appreciate the already existing understanding that observing a phenomenon could influence the phenomenon. more details: well.........ok, first of all, they are confusing two separate but related strands: wave-particle duality, and the uncertainty principle. so one is not "based on" the other. and second of all, influence of the obersever on the observed is NOT a quantum mechanics only phenomenon. historically, the early part of the 20th century saw some key experiments which brought into question whether we could seriously consider that something which we thought had a wave property now acted like a particle, and vice versa. so the either/or was gone. actually, they seemed to co-exist together in one experimental setup. and with that came the question: could there be a coherent theory that straddled both types of properties. and in the 1930's, we got an affirmative answer: there was a framework, odd as it seemed, that allowed us to see how we would detect the property "particle" in one setup, and "wave" in another. That was Heisenberg. Then Heisenberg asked about the "meaning" of the theory. Since the structure of physical theory had taken such an unexpected turn, he focused in on the newest oddity, that properties of a thing looked more like a pair-wise *operation* than a one dimensional scalar *value*: so position and speed once sounded like "*three* feet away" or "moving *20* MPH, whereas now it's more like (very, very crudely!!!!) "changed *from* three feet away *to* six feet away", or "energy jumped *from* three calories *to* six calories", and so forth. these operations had a strangeness when looked at pairwise, and made it appear one could not ascribe the *pair of properties* position AND speed of a given particle at any one time. so H went thru some thought experiments to show why this might be true, and they became dubbed as uncertainty relations, historically, because of the way the uncertainty relations were first presented, there was this interpretation that it was the act of measuring (observing) that caused the problem. whereas the modern view is that *pairs* of properties act more oddly than any *one* property taken in itself. so observer could also be some macroscopic measuring instrument, not just human consciousness. so thence all the observer/observed paraphernalia.