One of the weirdest theoretical implications of quantum mechanics is that different observers can give different—though equally valid—accounts of the same sequence of events. As highlighted by physicist Carlo Rovelli in his relational quantum mechanics (RQM), this means that there should be no absolute, observer-independent physical quantities. All physical quantities—the whole physical universe—must be relative to the observer. The notion that we all share the same physical environment must, therefore, be an illusion.
Such a counterintuitive prediction—which seems to flirt dangerously with solipsism—has been clamoring for experimental verification for decades. But only recently has technology advanced far enough to allow for it. So now, at last, Massimiliano Proietti and collaborators at Heriot-Watt University, in the U.K., seem to have confirmed RQM; as predicted by quantum mechanics, there may well be no objective physical world.
Yet, our perceptions of the world beyond ourselves are quite consistent across observers: if you were to sit next to me right now, we would describe my study in very similar, mutually consistent ways. Clearly, observers must share an environment of some sort, even if such an environment is not physical—i.e., not describable by physical quantities.
Possible solutions to this dilemma have been proposed. For instance, writing for this magazine last year, I maintained that physical quantities describe merely our perceptions and are, therefore, relative to each of us as observers. What is really out there, underlying our perceptions, is constituted not by physical but by transpersonal mental states instead. Perceived physicality is merely a representation of that surrounding mental environment, brought into being by an act of observation.
This isn’t a new view. In fact, it is very old. For instance, already in the early 19th century, Arthur Schopenhauer argued that the physical world of discrete objects in spacetime is merely a subjective representation in the mind of an observer. What is really out there is what Schopenhauer called the “Will”: transpersonal mental states with a volitional character, which transcend our ability to sense or measure. It is the volitional character of these states that explains the universe’s evolution according to causal chains; the universe moves and changes because it is compelled to do so by the patterns of its own underlying willing.
Despite the objections one might have to Schopenhauer’s ideas, they do seem to make sense of RQM’s counterintuitive predictions: physics was developed to describe perceptual states alone, not endogenous mental states such as volition. For this reason, physical descriptions are always observer-dependent; they don’t capture the world as it is in itself, but merely how it presents itself to each of us, given our respective point of view within the environment. Make no mistake: there still is a common environment of transpersonal volitional states, in which we are all immersed; it’s just that this environment is not what physics directly describes.
Making sense of RQM by inferring that our surrounding environment is essentially mental—a view called “objective idealism”—avoids solipsism. However, it carries with it a seemingly difficult problem: if what is really out there are transpersonal volitional states, then why do seeing or hearing feel so different from desiring or fearing? If my perceptions represent underlying states akin to desire and fear, why do I see forms and colors instead?
If only we could provide a compelling rationale for this qualitative transition, we would be able to leverage objective idealism to make sense of RQM and the latest experimental results. But can we? As it turns out, we very well can; even in more ways than one.
Over the past several years, Donald Hoffman’s group at the University of California, Irvine, has shown that our perceptual apparatus hasn’t evolved to represent the world truthfully, as it is in itself; if we saw the world as it really is, we would be swiftly driven to extinction. Instead, we see the world in a way that favors our survival, not the accuracy of our representations. In Hoffman’s analogy, the contents of perception are like icons on a computer desktop: a set of visual metaphors that facilitate one’s job by illustrating the salient properties of files and applications, but which don’t portray these files and application as they really are.
Approaching the problem from a different angle, Karl Friston and collaborators have shown that, if an organism is to represent the states of the external environment in order to properly navigate this environment, it must to so in an encoded, inferential manner. The reason is that, if the organism were to simply mirror the states of the external environment in its own internal states, it would not be able to maintain its structural integrity; its internal states would become too dispersed and the organism would dissolve into an entropic soup. Perceptual encoding is necessary for the organism to resist entropy and thus remain alive.
What both of these lines of argument suggest is this: the screen of perception is much more akin to a dashboard than a window into the environment. It conveys relevant information about the environment in an indirect, encoded manner that helps us survive. The forms and colors we see, the sounds we hear, the flavors we taste are all like dials: they present to us, at a glance, information that correlates—in a manner fundamentally beyond our ability to cognize—with the mental states of the environment out there.
Instead of having to feel the myriad mental states surrounding us—which would be akin to how a telepath would feel overwhelmed and disoriented in the middle of an agitated crowd—we encode them neatly in the pixels of the screen of perception.
Evolution has provided each of us with a dashboard of dials that inform us about the environment we live in. But we don’t have a window to look directly at what is out there; all we have are the dials. The error we make is in mistaking the dials for the external environment itself.
Physics models and predicts the behavior of the dials. Although we are all immersed in a common environment, each of us interacts with it in a different way, from a different perspective. Therefore, we each gather different information about the environment, and so our respective dials may not always agree. This doesn’t mean that there is no common environment; it means only that this environment isn’t physical.
For as long as we insist that the world, as it is in itself, must have the forms and contours of the images on the screen of perception, quantum mechanics will continue to be paradoxical. For as long as we believe that physical theory models the shared environment underlying our perceptions—as opposed to the perceptions themselves—quantum mechanics will continue to be puzzling. As discussed much more extensively in my latest book, there is only one reasonable way out: to regard our perceptions as a dashboard of dials providing salient, though indirect, information about a mental universe out there.