Resonator II (Detail) by Eric J. Heller. "In this image, a quantum wave builds up in a resonant cavity between the straight and curved walls, when waves are arriving from below. Most of the wave energy is reflected back, but a surprisingly large fraction of it gets through the tiny hole if the wavelength is just right to make the cavity resonant. Prof. Robert Westervelt and his research group invented the 'Westervelt resonator' around 1995 at Harvard University, for the purpose of investigating electron waves... The whole device is just a few microns across, or smaller than a bacterium."

If the wave function (or the state vector in the Schrödinger picture) were an ontological state that evolves continuously and predictably (between measurements if not always), then it would evolve in an intrinsically and completely differentiated spacetime. Continuous evolution (between measurements if not always) requires a world that is completely differentiated with respect to both space and time, whereas the quantum-mechanical probability algorithm implies that the spatiotemporal differentiation of reality does not go all the way down.

As said, those who wish to transmogrify the quantum-mechanical probability algorithm into an evolving ontological state, have to answer the question: why two modes of evolution rather than a single one? The reason this is a pseudo-question is that the actual number of modes of evolution is zero.

One pseudo-question leads to another... and another... and another...

For example, since the evolutionary paradigm is inconsistent with the incomplete spatiotemporal differentiation of reality that follows if the quantum formalism is fundamentally a probability algorithm, the interpretation of a quantum state as an evolving ontological state rules out that the quantum formalism is fundamentally a probability algorithm. If a quantum state is not fundamentally a probability algorithm, then one has to explain why certain mathematical expressions of the quantum formalism should be interpreted as probabilities. So far every attempt to explain this has proved circular.

In particular, the attempt to explain this via einselection (environment-induced superselection) relies heavily on reduced density operators, and the operation by which these are obtained — partial tracing — already presupposes Born's probability rule.

In addition one has to explain what the quantum-mechanical probabilities are probabilities of, or why they are probabilities of measurement outcomes.

Compare this imbroglio with the ease with which we can understand

Again, postulating an instantaneous physical state is the temporal equivalent to postulating a sharp position for every particle. Whereas the former postulate requires that the temporal differentiation of reality be complete, the latter requires that the spatial differentiation of reality be complete. In a relativistic world, the two postulates are inseparable. This comes to saying that not only Bohmian mechanics but every interpretation of quantum mechanics that construes the time dependence of a quantum state as the time dependence of an evolving instantaneous state, postulates features of reality that it declares, in the same breath, to be strictly unobservable — without ever bothering to explain why they are unobservable. (If quantum mechanics is fundamentally a probability algorithm, they are unobservable for the simple reason that they don't exist.)