On the meaning of "indeterminism" of Quantum Theory I was reading more into the details about the successes and failures(apparently none) of quantum theory. I have some very basic questions that do not require a mathematical answers. When quantum theory describes the indeterministic nature of things, does it mean that properties cannot be determined accurately or does it mean that properties are themselves random and take arbitrary (but quantized) values. Coming down to a specific example, lets consider the example of the measurement problem where by trying to look at the path of the electron in the double slit experiment, we change its course, the wavefunction collapses, and we say that we have already changed the system to a degree that we cannot say what it was like before we changed it. (I just saw this explanation in a youtube video by a Stanford physics prof giving lectures on basics of quantum mechanics). Now, I have a problem here. Lets me say there was a billiard ball, 'A', coming from some direction (electron) and i threw another one, 'B', at it (the photon). So if I knew the exact velocity and direction of 'B' and the coefficient of restitution, then by looking at the deflection in 'A' and its subsequent velocity, I could use newton's laws to find the original conditions of 'A'. Likewise, if I had equipment sophisticated enough to exactly produce photons of known properties and I invoke appropriate quantum mechanical laws, then can I not find what the electron was like before I disturbed it ..??? So from this point it looks to me that if I know what I am throwing at the object then I can also look at the object. Of course, I am wrong. But I need to know where. Has it got to do with the fact that we do not know how much the electron will absorb and emit? The problem still seems to me as the problem of not having the best possible technique to produce well predefined photons and subsequently measure the path of electron. A recent article, http://www.nature.com/ncomms/journal/v2/n8/full/ncomms1416.html which vindicates QT, says that more information from any extension of QT cannot be obtained and that QT is essentially complete. I am not doubting what they say, just wanting to understand it better. To be very literal, my question is - is it the fact that physical systems cannot be examined, even mathematically, beyond a certain limit? or is it that they don't really have well defined values and definitions but only once we observe they take up values, which will be different every time we try to observe? On a light note: I have this intuitive feeling that the wave-particle duality in some way corresponds to this indeterminism/uncertainty which we do not know in terms of equations yet.