Arguably most intractable philosophical question attached to Quantum Mechanics (QM) is that of Measurement. The accepted (a.k.a. Copenhagen) Interpretation of QM says that very act of sentient measurement determines outcome of measurement in quantum (microcosmic) realm. The wave function (which describes co-existing, superpositioned, states of system) "collapses" following an act of measurement.
It seems that just by knowing results of a measurement we determine its outcome, determine state of system and, by implication, state of Universe as a whole. This notion is so counter-intuitive that it fostered a raging debate which has been on going for more than 7 decades now.
But, can we turn question (and, inevitably, answer) on its head? Is it measurement that brings about collapse – or, maybe, we are capable of measuring only collapsed results? Maybe our very ability to measure, to design measurement methods and instrumentation, to conceptualize and formalize act of measurement and so on – are thus limited and "designed" as to yield only "collapsible" solutions of wave function which are macrocosmically stable and "objective" (known as "pointer states")?
Most measurements are indirect - they tally effects of system on a minute segment of its environment. Wojciech Zurek and others proved (that even partial and roundabout measurements are sufficient to induce einselection (or environment-induced superselection). In other words, even most rudimentary act of measurement is likely to probe pointer states.
Superpositions are notoriously unstable. Even in quantum realm they last an infinitesimal moment of time. Our measurement apparatus is not sufficiently sensitive to capture superpositions. By contrast, collapsed (or pointer) states are relatively stable and lasting and, thus, can be observed and measured. This is why we measure only collapsed states.
But in which sense (excluding their longevity) are collapsed states measurable, what makes them so? Collapse events are not necessarily most highly probable – some of them are associated with low probabilities, yet they still they occur and are measured.
By definition, more probable states tend to occur and be measured more often (the wave function collapses more frequently into high probability states). But this does not exclude less probable states of quantum system from materializing upon measurement.
Pointer states are carefully "selected" for some purpose, within a certain pattern and in a certain sequence. What could that purpose be? Probably, extension and enhancement of order in Universe. That this is so can be easily substantiated by fact that it is so. Order increases all time.
The anthropocentric (and anthropic) view of Copenhagen Interpretation (conscious, intelligent observers determine outcomes of measurements in quantum realm) associates humans with negentropy (the decrease of entropy and increase of order).
This is not to say that entropy cannot increase locally (and order decreased or low energy states attained). But it is to say that low energy states and local entropy increases are perturbations and that overall order in Universe tends to increase even as local pockets of disorder are created. The overall increase of order in Universe should be introduced, therefore, as a constraint into any QM formalism.
Yet, surely we cannot attribute an inevitable and invariable increase in order to each and every measurement (collapse). To say that a given collapse event contributed to an increase in order (as an extensive parameter) in Universe – we must assume existence of some "Grand Design" within which this statement would make sense.
Such a Grand Design (a mechanism) must be able to gauge level of orderliness at any given moment (for instance, before and after collapse). It must have "at its disposal" sensors of increasing or decreasing local and nonlocal order. Human observers are such order-sensitive instruments.
Still, even assuming that quantum states are naturally selected for their robustness and stability (in other words, for their orderliness), how does quantum system "know" about Grand Design and about its place within it? How does it "know" to select pointer states time an again? How does quantum realm give rise to world as we know it - objective, stable, certain, robust, predictable, and intuitive?
If quantum system has no a-priori "awareness" of how it fits into an ever more ordered Universe – how is information transferred from Universe to entangled quantum system and measurement system at moment of measurement?
Such information must be communicated superluminally (at a speed greater than speed of light). Quantum "decisions" are instantaneous and simultaneous – while information about quantum system's environment emanates from near and far.
But, what are transmission and reception mechanisms and channels? Which is receiver, where is transmitter, what is form of information, what is its carrier (we will probably have to postulate yet another particle to account for this last one...)?