 There is a close relationship between a no-collapse hidden-variable theory like Bohmian mechanics and a non-branching many-worlds theory like the many-threads theory. In Bohmian mechanics the wave function always evolves in the usual deterministic way, but particles are taken to always have fully determinate positions. For an \(N\)-particle system, the particle configuration can be thought of as being pushed around in \(3N\)-dimensional configuration space by the flow of the norm squared of the wave function just as a massless particle would be pushed around by a compressible fluid (the compressible fluid here is the probability distribution in configuration space given by the standard wave function). Here both the evolution of the wave function and the evolution of the particle configuration are fully deterministic. Quantum probabilities are the result of the distribution postulate. The distribution postulate sets the initial prior probability distribution equal to the norm squared of the wave function for an initial time. One learns what the new effective wave function is from one’s measurement results, but one never knows more than what is allowed by the standard quantum statistics. Indeed, Bohm’s theory always predicts the standard quantum probabilities for particle configurations, but it predicts these as epistemic probabilities. Bohm’s theory is supposed to give determinate measurement results in terms of determinate particle configurations (say the position of the pointer on a measuring device). (See Barrett (1999) and the entry on  Bohmian mechanics  for more details.)