The ceaseless flow of the present moment, the “now,” has long been a source of fascination due to a peculiar paradox at its core. From an individual standpoint, the present is paramount. It is the sole temporal domain where action and choice are possible, the only period we can truly experience or comprehend. Even memories and future aspirations are fundamentally constructed and processed within this immediate timeframe; their existence is solely in the now.
Yet, contemporary physics presents a contrasting perspective. In Albert Einstein’s theory of relativity, the concept of a universal “now” as commonly understood dissolves. All moments in time are considered equivalent, meaning events can be viewed as already concluded or yet to unfold depending on an observer’s frame of reference. The notion of a linear progression, a cosmic unfolding where reality sequentially emerges, is absent.
This presents a significant intellectual challenge for humans who perceive themselves as conscious, feeling beings. If “now” is an illusion, then the ability to influence the future through choices made in the present becomes questionable, as all events might be considered pre-existent. This view seems to eliminate a crucial avenue through which our immediate thoughts and desires could instigate change. By removing “now” from its central role, the universe may appear to diminish a fundamental aspect of our personal agency.
Motivated by this conundrum, the author explored whether an alternative perspective exists that could bridge scientific understanding with a cosmos that accommodates human choice. The investigation revealed a potential affirmative answer, contingent upon a radical re-evaluation of both reality’s nature and our place within it. As philosopher of physics Michel Bitbol notes, “The world is such that you cannot separate yourself from it.”
Quantum Paradoxes and the Observer
Exploring this alternative requires delving into classic thought experiments, such as one proposed by physicist John Wheeler in the 1970s. This experiment, a variation of the double-slit experiment, elegantly illustrates how the universe, and time itself, might operate in ways that diverge from common assumptions.
In the standard double-slit setup, photons are directed towards a barrier with two openings. The behavior of a photon appears to depend on whether its path is observed. When unobserved, a photon behaves like a wave, seemingly traversing both slits simultaneously. However, upon observation, it manifests as a particle, passing through only one slit. This phenomenon, termed “collapse” by quantum physicists, signifies a transition from probabilistic uncertainty to a definite state at the moment of measurement.
Wheeler significantly advanced this concept by posing a crucial question: what happens if the decision to observe a photon’s path is delayed until after the photon has already completed its journey? Decades of research have substantiated Wheeler’s prediction of the delayed-choice experiment: the observer’s subsequent decision demonstrably influences the photon’s trajectory.
Wheeler characterized this as a reversal of the conventional temporal order, suggesting that our present choices might affect not only the immediate future but also the past. Physicists have grappled with this and other quantum paradoxes, proposing theories such as parallel universes (multiverses) where all possibilities coexist, or postulating unseen influences like pilot waves that instantaneously connect disparate reality segments. For Wheeler, however, the lesson from quantum mechanics was profound: reality does not exist independently of observation. A particle remains undefined until observed, as its state prior to measurement is one of potentiality, not fixed definition. The act of questioning shapes the response received.
Wheeler extrapolated from this that if a phenomenon exists only upon measurement, then what we perceive includes its past as well as its present. He posited that our entire universe, encompassing past, present, and anticipated future, is continuously brought into being moment by moment through the answers to the questions we pose. A different set of questions, or a different sequence, would yield a distinct outcome. Wheeler encapsulated this idea as “it from bit,” asserting that the perceived particles arise from “information” we actively contribute to creating.
Wheeler’s insights laid the groundwork for the highly impactful field of quantum information science, now fundamental to technologies like quantum computing and cryptography. However, as this field expanded, physicist Christopher Fuchs, a former student of Wheeler’s, expressed concern that the discourse often treated information as an independent element, overlooking Wheeler’s core point that answers only emerge when questions are asked.
Fuchs sought to re-center the role of the experimenter, initiating a new interpretation of quantum physics from the 1990s, eventually termed QBism. This approach questions the implication of measurement outcomes being intrinsically linked to the act of measuring. Fuchs and his collaborators began reformulating quantum mechanics equations from a first-person perspective.
Their work utilized a Bayesian framework for probability, a method of understanding the world internally by constantly updating predictions based on past experiences rather than making definitive statements about objective reality. As Fuchs explains, “Probabilities are not things out in the world, but rather measures of what somebody knows.” This reformulation, undertaken by Fuchs and his fellow QBists, revealed that quantum mechanical relationships could be effectively expressed through this subjective lens. This process led to a significant revelation.
Central to quantum mechanics is the Born rule, established by Max Born in 1926, which typically provides objective probabilities for physical outcomes based on a particle’s quantum state. Inputting known information about a quantum entity, such as a photon, should yield the likelihood of a specific measurement result. However, within the QBist framework, the rewritten rule shifted focus from external objects to a method for connecting entirely personal probabilities—beliefs—across different experimental contexts.
Fuchs argues that quantum physics probabilities are not indicative of an external reality. Instead of acting like a flashlight illuminating the external world, quantum physics functions more like a manual or “handbook” for an individual, guiding predictions about likely outcomes based on specific actions taken. Consequently, another individual, possessing a different history of experiences and beliefs, might arrive at entirely different conclusions.
The notion that quantum physics primarily serves as a guide to personal experience rather than an objective reality might seem extreme. However, QBism’s credibility is strengthened by its ability to dissolve quantum mechanical peculiarities. The apparent “collapse” of a quantum state upon measurement, in QBism, is simply the physicist experiencing an outcome that prompts an immediate revision of their future beliefs.
Consider Wigner’s friend paradox, proposed by Eugene Wigner. In the conventional interpretation, a friend inside a lab measures a particle while Wigner, outside, is unaware of the result. The two individuals seemingly observe contradictory quantum states, suggesting that physical reality exists in opposing conditions simultaneously. However, if quantum states are understood as personal beliefs, this conflict becomes readily explicable. Similarly, Wheeler’s delayed-choice experiment does not necessitate temporal anomalies, as there is no independent particle “out there” to alter. Every measurement, regardless of its perceived temporal relation, is an individual experience that becomes real for that person upon obtaining the result.
QBism has faced considerable criticism, being labeled as nonsensical or confused, and accused of denying the existence of reality. However, stepping back from the subatomic realm to consider everyday human experiences—planting a tree, voting, reading a book, checking on a friend—it becomes less radical to suggest that our choices and actions can indeed shape outcomes, and that truth can be contingent on the questions we ask.
The Physical World as a Predictive Construct
Interestingly, neuroscientific research is arriving at parallel conclusions regarding general perception. The traditional “bottom-up” model of perception posits that we directly apprehend external reality; for instance, seeing a mug on a desk is a result of light from the mug reaching the eyes and signals being processed by the brain to form an image. However, accumulating evidence suggests that our experience is not a direct perception of the external world but rather a continuously updated internal model or prediction.
This framework, known as predictive coding, posits that the brain employs a probabilistic, Bayesian approach, constantly refining its understanding of the world as new sensory information emerges. Objects we perceive, such as mugs or cats, are essentially the brain’s “best guesses,” according to neuroscientist Anil Seth, influenced by individual history and beliefs. Seth states, “We will never see things as they really, really are,” adding that “It’s hard to know what that would even mean.” The widely publicized 2015 “dress incident,” where perceptions of its color varied drastically, serves as a potent illustration that individual interpretations of the world can differ significantly. If Fuchs’s QBist perspective holds, quantum physics reflects a similar principle—not as an objective lens on the universe, but as an enhanced system for processing experience. Even fundamental entities like photons or atoms are viewed as personal predictions, inseparable from the observer’s viewpoint.
A crucial distinction, however, lies in the underlying assumption. Most neuroscientists, like many physicists, tend to assume that despite differing subjective experiences, a stable, objective reality exists beyond our perception. Seth characterizes these internal probabilistic models—our conscious experience—as a “controlled hallucination,” implying we remain detached from the true physical world.
Yet, if this external landscape is absent, the implications of predictive coding shift dramatically. Fuchs’s central innovation is the assertion that no overarching truth exists; there is no “God’s eye” perspective irrespective of individual viewpoints. Instead of viewing our personal realities as mere hallucinations or models of a physical world, the argument is that these experiences are integral components of a different kind of reality, possessing their own causal efficacy. While Wheeler envisioned a universe composed of information, Fuchs emphasizes actions and their consequences. “If you don’t take the action, you have a different universe than if you do take an action,” Fuchs asserts, “And if you do take an action, it depends on which kind of action you take.”
This leads to the concept of the pluriverse: a dynamic network of interwoven perspectives, described by Fuchs as “a living community of nows.” Rather than comprising pre-existing, independent entities, this pluriverse is constructed from patterns of experience, continuously generated through choices and actions. It encompasses all elements that shape our perceptions and behaviors—ranging from the atomic and energetic phenomena of physics to deeply personal beliefs, irrational fears, and sensory encounters like the crunch of autumn leaves or the presence of monsters under the bed.
Bitbol suggests QBism offers a compelling “twist” on reality. Einstein’s general theory of relativity portrays reality as a four-dimensional block universe, a static construct where events are fixed in relation to one another but without any overarching temporal unfolding. In contrast, the pluriverse is depicted as akin to a jazz improvisation, a wild forest, or a vibrant crowd—an emergent, evolving collective endeavor devoid of a predetermined plan, with the inherent freedom to forge its own future. “It’s continual creation,” Fuchs observes. “Nature is being hammered out as we speak.”
This perspective aligns with a class of quantum interpretations where existence is contingent on viewpoint. Matthew Leifer, a physicist specializing in quantum foundations, notes that QBism adopts the “most radical possible way of implementing that,” suggesting no inherent reason for universal agreement. While Leifer views QBism as excessively extreme, he acknowledges it as “a coherent and consistent place to be.”
Intriguingly, QBism shares significant commonalities with enactivism, a philosophy of mind proposing that living organisms—be it whales, plants, bacteria, or humans—are intrinsically linked to their perceived environments. Enactivism posits that neither pre-existing environments nor independent organisms exist; instead, both emerge through the dynamic process of perception itself. Within this framework, the internal models described by predictive processing are better understood as action-oriented guidelines. Enactivists thus conclude that our perceptions are not mere representations or hallucinations but are inseparably tied to reality, as are the perceptions of all living beings. Cognitive scientist Ezequiel Di Paolo describes existence as “an ever-changing moment of creation,” where individuals collectively shape both themselves and their worlds.
Both QBism and enactivism advocate for a dynamic, open-ended cosmos built on novelty and freedom. While this vision is appealing, the absence of a stable underlying reality raises questions: what connects these diverse perspectives, and how does this differ from each individual existing in a self-contained reality?
In QBism, nothing is irrevocably fixed, not even the past, until a choice is made. However, a singular, unyielding rule governs all: the QBists’ reinterpretation of the Born rule, which dictates how the flow of predictions must cohere. “Quantum probabilities aren’t freewheeling,” Fuchs states. “They’re all tied together.” Adjusting one belief necessitates recalibrating another elsewhere, establishing fundamental constraints on the structure of experience. This rule, Bitbol adds, “exceeds us” in a sense, even as we remain integral to the picture.
Consequently, Fuchs strongly refutes the notion that QBism implies reality is purely subjective. What exists at any given moment encompasses interconnected beliefs and perspectives, alongside the statistical framework that binds them. This pluriverse represents a different form of external reality, composed of other perspectives with which we can only “bump into,” as Fuchs puts it. While we can influence each other, be surprised or frustrated by events, true understanding of another’s perspective or prediction of their actions remains unattainable.
Building Shared Realities
“People are literally experiencing different worlds,” Di Paolo concurs. “But, of course, that doesn’t mean we cannot share.” We navigate an evolving “meshwork” of possibilities. Through interaction and communication, our perspectives can converge, facilitating the construction of shared realities, whether cultural narratives or the precise framework of physics.
In this light, science itself becomes a form of shared perspective, a departure from conventional views that have long pursued an objective, universal understanding of reality. “That has been the dream of science,” Di Paolo remarks. However, he argues that stripping away all perspective would render meaningful discourse impossible. From scientific models of microscopic entities to cosmic phenomena like supernovae, our comprehension of the universe is not an objective, external landscape but rather a highly rigorous and expansive guide to experience, leading to the suggestion that physical reality itself might be the hallucination.
Fuchs and his colleagues are collaborating with enactivists to foster mutual insights. Enactivists delve into the meaning of perception and interaction, while QBists offer a mathematical framework for how these predictions and probabilities interrelate. The ultimate goal is to develop a novel scientific worldview that avoids dichotomizing the world into mechanistic particles on one end and isolated pockets of consciousness on the other.
Navigating these extremes are the participants responsible for creating the pluriverse. This includes physicists conducting experiments, but more broadly, all humans engage in perception, predicting and acting to shape their own worlds. This agency is not limited to human consciousness; enactivists extend it to all life forms, from plants reacting to sunlight to bacteria seeking chemical gradients. The question arises whether other structures or processes could exhibit a form of perspective, making choices and responding to outcomes. Researchers are discovering that even rudimentary biomolecular networks demonstrate a degree of agency, pursuing specific objectives. Fuchs, for one, aims to extend his approach to encompass all forms of agency, not just conscious human measurements, to better understand how our experiences contribute to “the stuff of the world.”
This brings us back to the concept of “now.” QBists and enactivists propose a reality that was not initiated by a singular Big Bang and left to unfold passively. Instead, it is continuously coming into being through “billions upon billions” of small creative acts, as Wheeler suggested, occurring all around us. This view positions us not as passive observers of reality, but as immersed participants. Through our choices and actions, moment by moment, we exert influence on what exists—and what will come next.