Rehabilitation is challenged by many slippery words whose meanings are endlessly debated. Even defining rehabilitation is difficult, and concepts such as disability, impairment, and participation all become diffuse as one gets closer. This is true more broadly in health; it cannot be defined. We seek concrete entities, but they elude us.
Physics has a similar problem. Once it was clear that matter was made of atoms. Then we discovered that there were nuclei and surrounding electrons. The electrons became diffuse, spread-out clouds. And now quarks and strings have arrived. High-energy physics encompasses many entities that become less certain the more one explores their nature. Photons, for example, may be particles or waves.
Since about 2000, Quantum Mechanics, the science of matter’s nature at the subatomic level, has evolved an approach to understanding the concepts. This post examines whether healthcare, particularly rehabilitation, can apply the principles underlying so-called Relational Quantum Mechanics to better understand the systems in which we work.
Table of Contents
“The probability distribution for (future) values of variables relative to a system S depend on (past) values of variables relative to the same system S, but not on (past) values of variables relative to another system S′.”
Carlo Rovelli. 2025.
The Stanford Encyclopedia of Philosophy
This is the main assumption in Relational Quantum Mechanics: can it help our understanding of illness, disability, and rehabilitation?
Introduction.
Elizabeth Barnes is a philosopher at the University of Virginia. In 2023, she published a book titled “Health Problems. Philosophical Puzzles about the Nature of Health.” It explores how we conceive health and well-being and their relationship to disability. Ironically, she developed early-onset Parkinson’s Disease after she had written but before she published her book.
Another philosopher, Havi Carel, has examined a similar issue. Havi Carel suffered from a progressive, disabling lung condition before writing and reflecting on these topics, for example, in her book titled “Phenomenology of Illness”. Both writers highlight the lack of clear, context-independent definitions of the concepts used. They discuss the repercussions of conceptual ambiguity.
Models of health and quantum mechanics share several features. Both are concerned with objects, concepts that are not tangible (“perceptible by touch”, “clear and definite; real”, OED). Subatomic particles cannot be seen or felt, and concepts such as impairment, disease, or disability are equally intangible.
Both concern systems in which objects interact. Subatomic particles interact with one another, eventually forming higher-level systems such as atoms, molecules, cells, and bodies. In rehabilitation, two interactions interest me. Biopsychosocial concepts such as pathology, disability, and social roles interact to generate higher-level concepts such as health or illness. I will not consider this. I am interested in inter-personal interactions, the nature of personality, and the effects of limited interactions.
Quantum mechanics.
My interest in physics started a few hours before I also discovered biology, and although biology and medicine ultimately won out, I have retained my interest in Physics. Recently, I discovered Carlo Rovelli’s work, particularly two books: “Helgoland” and “Reality Is Not What It Seems.”
Carlo Rovelli’s books delve into the nature of reality, focusing on quantum mechanics and examining the history and evolution of key ideas. They highlight that our human view of reality has embedded in us ideas about physical concepts that do not apply at the subatomic scale.
Most people recognise the word quantum. They might be aware of quantum computing, have marvelled at the paradox of Schrödinger’s cat, or refer to a “quantum leap,” which, incorrectly, implies a huge step change. They may also be aware that quantum phenomena are a part of physics.
Contrary to popular use, a quantum is the smallest possible difference between two measures of a physical phenomenon. Even time is not continuous, but changes in minute steps, and each step is a step change without any intervening level.
Quantum mechanics is concerned with how matter is structured and behaves at the level of its building blocks. For example, how do electrons interact? Quantum mechanics has established that many particles exhibit both particle-like and wave-like properties, depending on the circumstances.
Relational quantum mechanics.
Along with many others, Carlo Rovelli developed Relational Quantum Mechanics. Interested readers can learn more here. As I read and reread the books, I suddenly realised the ideas might apply to health and rehabilitation. This post is the result.
Relational quantum mechanics challenges three widespread assumptions:
- A physical object’s properties are stable and will be observed or measured identically by all observers.
- A physical object will retain those properties even when it is not being observed or measured.
- An observer of the particles is independent of them and, usually, equated with consciousness.
These assumptions are based on our experience with large objects comprising billions of atoms. We also assume that ‘observing’ something is a passive activity that does not affect the observed object; we usually also assume the observer is conscious.
Relational Quantum Mechanics has different assumptions.
- Interaction effects are constant, but objects are not.
If System A interacts with System B, the interaction will be the same as it was last time System A interacted with System B. However, if System C interacts with System B, the interaction can be quite different, although the C-B interaction will be similar to earlier C-B interactions.
Therefore, the apparent properties of System B differ when interacting with System A from when interacting with System C. Interaction A-B is not the same as interaction C-B. Second, if System B is not interacting with any other system, it has no properties. Lastly, objects are only real if they interact with other objects. - There is no observer.
There is an interaction between two systems. One system might be considered as ‘an observer’, but it is the relationship or interaction that is important. There is no privileged status of observer or observed.
Thus, at the level of the fundamental particles making up the universe, reality is only a sequence of events as objects or systems interact. It is the specific interactions, not the interacting objects, that constitute a consistent reality. When an object is not interacting, its properties are indeterminate.
Constancy concerns interactions, not systems.
Relational quantum mechanics hypothesises that interactions between two objects are always the same, but the objects do not necessarily interact with other objects in the same way. Does this insight apply to humans and help our understanding of rehabilitation?
People can be considered social objects that interact with other people through their behaviours – communication, physical actions, tone of voice, etc. Personality characteristics are the main properties associated with a person. Personality is a nebulous concept encompassing the style and content of an interaction; we used words such as friendly, distant, aggressive, approachable, peculiar, etc. I discussed this matter in depth in a post on personal factors in rehabilitation.
Person A’s personality will be described reasonably consistently by person B in terms of their interactions (A & B). However, person C may give a markedly different description of person A, based on their interactions (A & C). Neither description is correct; perceived personality depends on each participant’s specific characteristics.
Naturally, when considering human behaviours, many other factors will influence them, such as relative roles (i.e., social context) and physical context. Nonetheless, the personalities of the two people will make a significant contribution. For example, in a team, one person may interact very differently with one member compared with another, potentially leading to team malfunction.
More generally, all a person’s behaviours are influenced by the context, including past experiences. Unfortunately, legal systems and other organisations, such as those providing support to people with a disability, have a fond belief that properties such as strength, walking endurance, and the ability to dress are fixed abilities.
They obviously are not. For example, when considering levels of consciousness and its emergence in people with prolonged disorders of consciousness, families may elicit behaviours not seen during interactions with staff. More mundanely, most bodily functions fluctuate and are affected by motivation, fatigue, etc.
In summary, we should accept that the ‘properties’ associated with personality, manifest through a person’s behaviour (i.e. their interactions), may vary according to the interaction. We should also remember that many contextual factors affect a person’s behaviour; behaviour and its implications should not be considered as fixed.
Event constancy
The flip side of an object’s variable properties in different interactions is the consistency in its properties when the events are the same. A photon always causes a Crookes radiometer to rotate and gives a diffraction interference pattern after passing through a slit.
The same is true of human social interactions. Personality is not a single construct; it encompasses different aspects. Nonetheless, despite some variability around a mean, each person will give a consistent picture of their personality when interacting with an individual, which will differ from descriptions given by other individuals after an interaction, but the difference will be consistent.
It is also likely that non-social behaviours, such as walking and personal care activities, are consistent in one situation but may differ consistently in another. The interactions are then not only with people but also with objects.
Events.
Events, dear boy, events.” It may not be true (see here), but supposedly Harold Macmillan said this when asked what the biggest challenge of being Prime Minister was. His response suggests that a leader’s life consists of a sequence of events.
Relational quantum mechanics suggests that the ‘life’ of a subatomic particle can be considered as a sequence of interactions with other particles, each interaction being an event. The properties of a particle in an interaction are determined by the other particles involved in the event. However, between events, the particle has no properties because it is not related to anything.
Observation is an event, one where the object interacts with another object, self-identified as the observer; in fact, all objects involved in an event are equally observers and observed. Measurement is an event, and the result observed depends on the nature of the system or systems involved.
Thus, observers are not external to any observed event; the extent of any effect they may have will vary. This is widely recognised in healthcare research where features such as inter-rater and intra-rater variability are measured. Moreover, the influence of the observer on the patient is recognised, leading to the use of double-blind, randomised controlled designs. In routine clinical practice, these aspects of observation and measurement are overlooked, forgotten, or ignored, and clinicians frequently draw invalid conclusions from their observations.
Events and existence.
One natural consequence of assuming that properties are constant and the same everywhere is to assume that the object’s properties continue to exist when not observed or, more precisely, when not interacting with another object. For example, we assume that the most distant manmade object in the universe, Viking 2, has (more-or-less) the same mass even though we cannot possibly measure it.
Quantum mechanics suggests otherwise. We can only conclude that something is real, that it exists, if we can observe an event involving it.
The Higgs boson was hypothesised in 1964, but 38 years elapsed before its existence was confirmed in high-energy experiments that revealed interactions (events) that had no simpler explanation. Another particle, the graviton, has not yet been identified, though gravitational waves have been detected, and no one doubts the existence of gravity; the existence of a graviton remains unproven.
The main relevance to the human condition is the crucial role social interaction plays in confirming our beliefs about ourselves. If our presence and attempts to communicate with others are ignored, we might doubt our worth to others and whether we are a person.
Philip Pullman explored this in Northern Lights, Part One of His Dark Materials. Witches could be so non-interactive that no one realised they were present. More realistically, the hero Will was a past master at being inconspicuous through non-interaction. Ursula le Guin also explored a similar theme in The Farthest Shore, the third Earthsea book. The dead could not (or did not) interact with each other or with living people.
Synthesis
Relating the features of the smallest known things in the universe to human experience and rehabilitation may be a huge leap (not a quantum leap!), but it gave me a different perspective that might help others.
Quantum relational mechanics suggests that the only reality at the subatomic level is the ongoing series of events affecting subatomic particles. There are no objects, only indeterminate particles/waves that are constantly interacting with one another.
Most stories, whether in novels or transmitted orally, relate a sequence of events. There are only a few fundamental plots; all involve events. Moreover, most social conversations concern events, directly or indirectly, such as who did what with whom, when and where. Third, we describe ourselves and others primarily in terms of roles and relationships, which are based on events and social interaction. Lastly, a low level of social interactions is associated with loneliness, which has adverse effects on an individual’s health.
This suggests to me that a person’s reality is also based on a long series of events, with almost all events mainly concerning interactions with other people. This is the basis of Narrative Medicine, an approach to healthcare that is very well suited to rehabilitation. At very low levels of social interaction, an individual may start to question their existence, not literally, but as a worthwhile person respected by others. Esteem in the eyes of others is one of Maslow’s five motivational needs.
Thirdly, it normalises personality variability. Some people feel that personal characteristics are immutable. Although totally different, the way that fundamental and inanimate particles interact can differ significantly, depending on the other particle(s) involved, so we should not be too surprised if perceived personality differs when different individuals describe the same person.
Conclusion
I do not suggest that the parallels I have suggested between Relational Quantum Mechanics and human social interactions lead to any valid conclusions. They are analogous, metaphorical comparisons that might stimulate new ideas, alter perceptions, or increase insight.
My synthesis has increased my concern that optimising social interaction should be the main goal for rehabilitation with every patient, because “a person’s reality is also based on a long series of events, with almost all events mainly concerning interactions with other people.” Consequently, we should explore Narrative Medicine: how can we incorporate it into rehabilitation, and does it improve patient outcomes?