**hes@ecsvax.UUCP (Henry Schaffer)** (09/29/85)

> Quantum physics seems to deal more with probabilities than randomness, > since events can happen spontaneously without cause, but the event that > occurs occurs with a certain probability. This is not true randomness, > since it is probability that guides what events occur. > > Scott Southard > <southard@unc> I either disagree with this distinction - or perhaps I don't understand the point. From a statistical point of view the possible outcomes of a random process have probabilities of occurring, so there is no conflict between randomness and probability. (However, it is not correct to say that probability "guides" the outcome, rather it describes. --henry schaffer

**gwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>)** (10/02/85)

This quibbling over the distinction between randomness and probabilities is beside the point. Quantum mechanics has the additional feature, not found in classical probability theory, of addition of complex probability amplitudes when possible alternative system states are considered. This makes the real probabilities not obey the classical (Bayes) rules, which raises some real questions about what it all means. (I hope I can forestall responses that do no more than state an operationalist frequency interpretation of the resulting probabilities; I know that already, thank you.) The interesting questions are "Why probability AMPLITUDES?" or more generally "Why aren't the classical laws of probability being obeyed?" The reason for asking the latter is that the classical laws are a direct result of counting alternative outcomes, which somehow doesn't work for QM (quite apart from the issue of whether identical particles are distinguishable). Note that I am not asking whether it works, but why it works. The trouble with the prevalent attitude that every theory is just a mathematical model is that such an attitude makes one quit trying to understand things; instead one just starts cataloging their behavior.