On causality

Cause and effectCausality is one strange concept. It is absolutely essential to our understanding of the so-called “manifest image” of the world, i.e., the world as perceived and navigated by human beings. (The distinction between the manifest and the scientific image was introduced by philosopher Wilfred Sellars.) It is crucial for us to distinguish between events that happen because (i.e., are caused by) other events, vs things that appear to be the result of chains of cause-effect but really aren’t. We think smoking, statistically speaking, causes cancer, meaning that there are physical events that make it more likely that if you are a smoker you will get cancer. But when a few years ago someone showed a statistically significant correlation between number of births in London and frequency of storks flying overhead, nobody cried out for a revision of human biology textbooks…

When it comes to the “scientific image,” i.e., how science tells us the world is, things are more complicated. Talk of causality is all over the place in the so-called “special sciences,” i.e., everything other than fundamental physics (up to and including much of the rest of physics). In the latter field, seems to me that people just can’t make up their minds. I’ve read articles by physicists, and talked to a number of them, and they seem to divide in two camps: those who argue that of course causality is still crucial even at the fundamental level, including in quantum mechanics. And those who say that because quantum mechanical as well as relativistic equations are time symmetric, and the very idea of causality requires time asymmetry (as in the causes preceding the effects), then causality “plays no role” at that level.

Both camps have some good reasons on their side. It is true that the most basic equations in physics are time symmetric, so that causality doesn’t enter into them. But it is also unquestionably true that we have to somehow explain the arrow of time and the fact that things do very much appear to happen one after the other. While we move freely back and forth the three spatial dimensions, we definitely don’t do that along the fourth, temporal, dimension.

Three possible solutions to this conundrum are: I) to say that causality is an “illusion,” part and parcel of the manifest image, but not really a scientifically viable concept; or II) to claim that causality somehow emerges from basic physics (whatever “emergence,” a philosophically controversial concept, means); or III) to argue that causality is fundamental and that there is something incomplete about quantum mechanics and general relativity, and that’s why it needs to be “added by hand,” so to speak, in order to describe how the world actually works.

This, in turns, depends on how one conceives time — the element that, after all, is needed for causality. For instance, Brad Skow adopts the “block universe” concept arising from Special Relativity and concludes that time doesn’t “pass” in the sense of flowing; rather, “time is part of the uniform larger fabric of the universe, not something moving around inside it.” If this is correct, than “events do not sail past us and vanish forever; they just exist in different parts of spacetime … the only experiences I’m having are the ones I’m having now in this room. The experiences you had a year ago or 10 years ago are still just as real [Skow asserts], they’re just ‘inaccessible’ because you are now in a different part of spacetime.

It isn’t entirely clear what this view does with respect to causality, and it doesn’t seem to explain why we feel like time is something very different from space. Moreover, it doesn’t explain, say, the manifest image-level difference between causation and correlation. None of this means that the block universe concept of time/causality is wrong, but it does mean that there are serious pieces of the puzzle still missing.

Lee Smolin has a very different idea of time, and therefore of causality, as I have explained in detailed in the past. For him quantum mechanics and relativity are indeed incomplete (on this everyone seems to agree, including string theorists, who vehemently reject Smolin’s approach), time is fundamental, and so is causality. Indeed, he goes as far as saying that the laws of nature emerge from the specifics of causal interactions at the fundamental level, not the other way around.

In philosophy too, causality has always been a messy business. Famously, according to David Hume, it is something we add onto our perception of the fabric of the universe, and that may not be inherent in it. As the excellent Internet Encyclopedia of Philosophy article on Hume and causality puts it: “Whenever we find A, we also find B, and we have a certainty that this conjunction will continue to happen. Once we realize that ‘A must bring about B’ is tantamount merely to ‘Due to their constant conjunction, we are psychologically certain that B will follow A,’ then we are left with a very weak notion of necessity. This tenuous grasp on causal efficacy helps give rise to the Problem of Induction — that we are not reasonably justified in making any inductive inference about the world.”

However, it is not at all clear whether Hume thought that this is all there is to causality, or rather simply all that an empiricist approach to causality allows us to say, and Hume scholars disagree on this point.

Modern philosophers have developed a number of different theories of causation (and of time), that attempt to take into account what we have learned from science, and particularly physics, and make sense of it. It’s not an easy task, to put it mildly.

One of my favorite modern ways of thinking about causality (though, of course, it has its critics and drawbacks) is the co-called conserved quantity theory of causation. Here are the two major versions, according to the Stanford Encyclopedia of Philosophy (if you keep reading that article, you will also see a number of standard objections raised against it, the proposed responses, etc.):

P. Dowe’s version (1995, p. 323):

CQ1. A causal interaction is an intersection of world lines which involves exchange of a conserved quantity.

CQ2. A causal process is a world line of an object which possesses a conserved quantity.

W. Salmon’s version:

Definition 1. A causal interaction is an intersection of world-lines that involves exchange of a conserved quantity.

Definition 2. A causal process is a world-line of an object that transmits a nonzero amount of a conserved quantity at each moment of its history (each spacetime point of its trajectory).

Definition 3. A process transmits a conserved quantity between A and B (A ? B) if it possesses [a fixed amount of] this quantity at A and at B and at every stage of the process between A and B without any interactions in the open interval (A, B) that involve an exchange of that particular conserved quantity.

Here is a list of universally conserved properties in interactions between elementary particles:

  • energy
  • linear momentum
  • angular momentum
  • electric charge
  • baryon number
  • electron-muon-tauon number
  • lepton number

All of this, of course, has profound implications for both science and philosophy, but also for the way we should think about the world, i.e., these considerations affect both our scientific and our manifest images of the world.

Recently, I’ve began to think of causality as somewhat similar, in its manifestations, to physical forces, such as gravity. While gravity is universal, meaning that it acts in every point of the universe, so that in theory we are subject to the gravitational pull of every body in the cosmos that has mass, in practice we only need to be concerned with the gravitational effects induced by sufficiently massive bodies laying close enough to us. Our everyday life is affected by the gravity of Earth, the Moon, and the Sun, and little else. You need not worry about the gravitational pull of, say, the Andromeda galaxy because, even though it’s huge, the thing is so far from us that its orbital period is billions of years, so that it has no measurable effect on your existence. You also don’t need to concern yourself with the gravitational influence of people around you, because while they are nearby, their mass is just too small to do anything of consequence to you.

Perhaps causality is like that: while it makes sense to think of cause and effect as a universal phenomenon, with everything connected to everything else, for any practical purpose we are free to take into account only local causal interactions, all the other ones being dampened or overridden so to become irrelevant. It remains to be seen what such view would do to radical metaphysical notions like universal determinism (and consequent reductionism), or to controversial ones such as top-down causation (and consequent anti-reductionism).

You would think that this is an obvious area of inquiry where scientists and philosophers should come together. It isn’t, in my opinion, simply a matter of letting science tells us how things really stand. For one thing, because I’m confident that a fundamental physicist, a non-fundamental one, a biologist, and a social scientist would have very different views of what “science tells us” (indeed, as I mentioned above, even fundamental physicists vehemently disagree among themselves, so…).

Nor, of course, is it a question of calling the philosophical cavalry to explain to the naive scientists how they ought to think about the matter. That would be presumptuous to the level of silliness.

But why isn’t the question of time, or that of causality, a straightforward scientific issue? Why do we need philosophers to begin with?

One answer would be because philosophers have spent literally centuries thinking about these issues, much more so than scientists, and so there is likely something to learn from the best proposals they have put forward so far.

But that’s not actually it, or at the least, it isn’t the whole story. I think time and causality are a perfect example of the power of “sciphi,” if you will, because the issue isn’t just one of discovering facts about time and causality, it is to develop an understanding of these concepts that allow us to keep pursuing Sellars’ overarching objective: “to formulate a scientifically oriented, naturalistic realism which would ‘save the appearances'” [1]. The more I think about it, the more it seems to me that the (or at the least a major) goal of philosophy is precisely to articulate a mapping function that connects the scientific image — which only science can provide us — with the manifest image, which we simply cannot do without as cognitively limited biological creatures of a certain kind (and that includes scientists, obviously).

[1]  “Autobiographical Reflections (February 1973),” p. 289 in Action, Knowledge, and Reality: Studies in Honor of Wilfrid Sellars, H-N. Castañeda (ed.), Indianapolis: Bobbs-Merrill, 1975: 277-93.

125 thoughts on “On causality

  1. marc levesque


    I liked a lot of what Jung had to say. Sure I disagree with some of what he wrote but I wouldn’t discredit the rest for that. Same for anyone else I’ve read, and sometimes rather than interpretations or theories what I like has mostly to do with the choice and treatment of the subject matter.

    Liked by 1 person

  2. Robin Herbert

    I like the “emergent space” ideas because it is the second of my crackpot ideas where I might accidentally turn out to be somewhat right. I have been saying for years that the idea of a “graviton” made no sense at all and that rather there should be a spaciton, (or a chronospaciton *) although I have not even tried to work out the maths of such an idea.

    I am also good with the name Herbert Boson 🙂

    Liked by 2 people

  3. brodix


    “Sometimes it does seem more meaningful to speak of a high level behaviour causing low level behaviour, rather than the other way around.”

    Wouldn’t top down and bottom up be two sides of the same reality? Nodes and networks. We are predisposed to think of the nodes as ontologically real and the networks as emergent, but that is the western philosophic focus on the object as separate from context, rather than a reflection of it. Not only is it at the root of our political beliefs, but our concept of time as well. We tend to equate the future with being in front of us and the past behind us, as we see ourselves as moving through our context. The eastern view is the past is in front, because it is known and can be seen, while the future is behind, as it is unknown and cannot be seen. Which is how we do exist in context, as information of past events comes to us and then passes to further observers.

    “although it is difficult to think of a compression wave travelling through a gas as an ontological “thing”.’

    At what level do “things” exist? As Arthur observed previously, entanglement is potentially explained as two points on the same wave. Which would mean the wave is foundational to the “particles.” It is easier for us to think of particles as real and waves as effect, but is that just intuition? We evolved as organisms largely built to grasp and manipulate objects, like rocks, sticks, tools, etc. Yet they have no reality outside of the context which created them. They are intersection points of energies/waves. Nodes in a network. They are the effect of cause. If cause is an emergent description, effect certainly is as well.


  4. brodix


    If you want a “crackpot wars,” I’ll take the other side of that and argue space is as foundational as it gets.

    If you remove all physical properties from space, even the dimensionless point as an ideal of location, then it would have two non-physical qualities left; Infinity and equilibrium.

    Infinity because there would be nothing to define or limit it. Nothing has no limits, even location. As soon as there is something, it needs definition and thus limits.

    On the other hand, equilibrium is implicit in the premise that clocks slow and distance shrinks in frames moving through the vacuum, as the frame with the longest distance and fastest clock would be closest to the equilibrium of this “vacuum.”

    Space is the ultimate freebie, because it doesn’t need cause.


  5. synred


    although it is difficult to think of a compression wave travelling through a gas as an ontological “thing”.

    In QFT electrons and protons are waves (excitation of ‘fields’) an if waves aren’t “things’ nothing is! :

    Liked by 1 person

  6. Robin Herbert

    Hi Brodix,

    Why doesn’t empty space need a cause? Practically everybody from Plato onwards has assumed that empty space needs a cause – how do you get uncaused empty space? What is the dimensionality of foundational space (Hilbert Space maybe)?

    Liked by 1 person

  7. synred

    The medium is different — water vs. the seemingly more abstract field. And, of course, the QFT wave is quantized which is very important, e.g., leading to the Pauli exclusion principle and hence to the existence of what we call ‘objects’

    but an electron is just a wave. I would say water waves have ontological status, they are particles moving in a coordinated way. Wouldn’t you say light exist? That’s a wave. So do electrons exist, they are also waves (but quantized so they come fixed numbers and can’t overlap).

    I’m not saying electrons don’t exist, but that water waves do. The narrow meaning of existence — applying it only to things you can kick — is not viable. My comment was meant to be a reduction ab absurdum way of putting it, i.e., if water waves don’t ‘exist’ neither o ‘electrons, protons, neutrons’ or chairs.

    Kicking a wave is problematic, but they can knock you over.

    Or people. We are more analogous to a soliton [a] than a machine. With matter flowing through us in a complicate self-reinforcing pattern We are a non-linear wave phenomena. If waves don’t ‘exist’ than neither do we.

    [a] Mathematical solitons are eternal, but the kind that flow up the river in Edinburgh die as do we.

    For an attempt at humor see: Quantum Transubstantiation here:


    It’s not that easy to make QFT funny…

    Liked by 1 person

  8. brodix


    Plato, accurately or not, was the progenitor of Platonism, of which I’m not a fan.

    Three dimensional Euclidian space is not foundational to space. It is a mapping device, essentially the xyz coordinate system. It is no more foundational to space than longitude, latitude and altitude are foundational to the surface of this planet. So higher dimensional constructs are not higher orders of space, but higher orders of our aptitude for abstract thought.

    If Euclidian space is foundational to the nature of space, than why didn’t nature start off with straight lines and right angles? Why did she start with the complicated, hard to model stuff, like fluctuations, waves, then on to spirals, elliptical, orbits, orbs, etc. and only get to straight lines and right angles when builders found flat surfaces are handy to stack angular blocks on and theorists started analyzing them?

    Just because we start off in kindergarten with a sheet of paper, pencil and ruler, doesn’t mean nature does. Order is emergent with the dynamic processes it serves to model. Remember abstraction means to abstract. It isn’t some secret portal into the mind of God.

    As I’ve argued before, a dimensionless point is mathematically self-negating, as it is a multiple of zero. Yet as an abstraction of location, it is a more useful construct than the fuzziness of some minimal dimensionality. The problem is it becomes a blank slate for all sorts of speculation.

    Then that speculation becomes dogma to various schools of thought. If you really want to understand how math really functions, you need to also study how the mind and the group function.


  9. victor panzica

    Human beings deal in intuitions or “factuals” like rocks are real and hard, gravity makes us weigh something and make us feel heavier when we are tired. Waves are not “factuals” until we apply mathematics which is actually a system of translations that are preserved. Clocks are finite objects or machines, even like the highly accurate clocks in GPS satellites that let us know where we are within inches any place on earth. If we start at 0ne and keep dividing or multiplying by two eventually we approach zero or infinity respectively? But when do we reach either?….When we stop dividing or multiplying or cease our finite counting procedure. Whether talking waves of water particles, air particles or asteroids in space, what underlies any wave behavior is really energy and mathematics allow us to make waves real things. Tools like mathematics allow us to take factual objects and extend them into initially “counterintuitives” like waves that we become familiar with to the point of their reality. Nature of course is not one, two, three four….circles and straight lines; but elliptical orbits and fractal biological shapes. Mammalian vision systems do detect vertical movement, edges etc. which civilized man extracted into fulcrums and vertical columns on temples.

    Human beings like all animals are endowed with a survival instinct which is really man’s original sin the translates in Western Civilization into drives like comfort and safety along with success, pride, social status etc. Structures like the amygdala sit in our ventral visual stream and mediate our emotions and survival instinct. The dorsal visual stream translates our perception of nature and beauty along with religion, like Kant sitting in the cathedral staring at the fresco filled ceilings. There are religions in the world which believe in total surrender of the survival instinct. Sam Harris has devoted his latest blog to this. Don’t argue, check the neurological facts.


  10. synred

    Waves are not “factuals” until we apply mathematics which is actually a system of translations that are preserved

    Waves seem pretty real to me. Ask the people of Fukuhima or Thailand who got hit by big ‘uns. Or those of us who were here in the bay area on Oct 17, 1989.

    During the 9.2 in in Anchorage, Alaska, in 1964, there were ocean sized wave rolling down the streets

    I couldn’t find the ‘ater like waves propagating down a street I saw on TV in 64. They may indeed have been water waves resulting from liquefaction.

    Anyway there’s no doubt waves caused the damage!


  11. synred

    Of course waves have energy. So does a rock laying on the ground — temperature and mass.

    That waves have carry energy makes them real.

    Reminds me of a phrase I hate from pop sci — ‘pure energy’. By that the authors of these tombs mean photons/light — i.e., waves. There is no such thing as ‘pure energy’ — some thing has to carry the energy. There are no things w/o energy and no energy w/o things.

    Liked by 1 person

  12. brodix


    “There is no such thing as ‘pure energy’ — some thing has to carry the energy. There are no things w/o energy and no energy w/o things.”

    Consider the implications of that dichotomy. Energy will always manifest as form/information, even as basic as frequency and amplitude of the wave. Conversely, there can be no form/information that is not manifested by some amount of energy. So no platonic form.

    Now energy, being energy, is dynamic, or potentially so. So it is regularly changing form. So the energy goes from prior to subsequent forms. While these forms coalesce from the field of potential energy and eventually dissolve back into it.

    So the difference between the energy and the “thing” it manifests is they are opposite directions of time. The energy goes past to future, as the forms go future to past.


  13. Coel

    Just to echo synred, since this seems misunderstood in some accounts (and not just in Star Trek movies!):

    There is no such thing as ‘pure energy’ — some *thing* has to carry the energy.

    The term “energy” is a commentary about a thing, not a thing. It is like the term “tall”. We can describe a person or a tree as “tall”, but there is no ontological entity, no fundamental particle, that constitutes “tallness” or “energy”.

    That’s why I don’t think that an account of “exchange of a conserved quantity” such as energy can be an actual account of causation at its most basic, at best it can be a higher-level commentary about causation. One can give any number of higher-level commentaries about causation.

    Liked by 2 people

  14. brodix


    Yet are those “commentaries” consequential? Does the “thing” exist without them? Does a person with zero height exist? To what extent are they the sum of those commentaries? In which case, it would seem the “thing” is a higher level commentary, as well. So yes, “causation” is simply a generic concept, if it doesn’t refer to an actual relationship. Though the line of causation, say between one’s parents heights and one’s own, might be a little less direct than between kicking a ball and it flying away.


  15. synred

    Well I would regard properties like energy as real enough. Maybe it’s all in what you mean by ‘ontological’. I agree that trying to define causation by transfer of a conserved quaintly makes no sense. By definition of ‘conserved’ can go either way in time. It means does not change!

    I’m inspired to write a story called ‘Causality — A Fable of Many Worlds” which will dramatically illustrate how time direction can ’emerge’.

    It adopt ‘many worlds’ QM view to maintain reverbility. Coel’s view of relying on QM measurement theory is in someway more satisfying as time direction is built into the theory. On the other hand it is built-in ad-hoc. There is no dynamical explanation.

    I don’t like ‘many worlds’ and believe it is actually inconsistent with the Born probability rule. Oxford philosophers and physicist jump through hoops trying to derive Born rule. Mostly they sneak it through the back door, covered in so much math you can’t tell where it came from. If you take ‘many worlds’ at face value, the Born rule will be violated from the perspective of an ‘observer.’

    On the other hand Copenhagen/von Neumann picture just adds the Born-rule by hand.

    The story will not be done before this thread withers away. I may post the raw intro here, if anybody expresses the slightest intro. Eventually, it will turn up on skeptical reviews.


  16. synred

    From: Arthur Snyder [mailto:synred@sonic.net] Sent: Thursday, August 18, 2016 8:31 AM To: ‘Plato’s Footnote’ Subject: RE: [New comment] On causality

    Waves are not “factuals” until we apply mathematics which is actually a system of translations that are preserved

    Waves seem pretty real to me. Ask the people of Fukuhima or Thailand who got hit by big ‘uns. Or those of us who were here in the bay area on Oct 17, 1989.

    During the 9.2 in in Anchorage, Alaska, in 1964, there were ocean sized wave rolling down the streets

    I couldn’t find the ‘ater like waves propagating down a street I saw on TV in 64. They may indeed have been water waves resulting from liquefaction.

    Anyway there’s no doubt waves caused the damage!


  17. synred

    Holding something in your hand is your standard for ontological status? So air is not real? No wonder you don’t think sound is real.

    A wave can knock you flat or knock down your house. Real enough for me! Do you think light is real? You’d be hard pressed to find a rock and pick it up w/o light (not impossible but hard).

    And you are made of waves that obey the Pauli exclusion principle and make you appear solid. Your very hand is a wave. If waves aren’t real you are real. Are you real?

    Even at the atomic level your not the same atoms for long. At the quantum level of quarks and leptons it’s pure wave. Your hand is a pattern that atoms flowing through and the atoms themselves are waves.



  18. Robin Herbert

    I think, though, that we are really talking of different sorts of things – compression waves running through a gas and an electromagnetic wave. Going back to my little dots scooting around the screen I could give a virtual “push” from one side of the box and watch a compression wave pass through the dots and I could describe it with a superficially similar kind of maths, but I can watch the macro and micro behaviour at the same time and there is nothing mysterious about what is happening with the compression wave through gas. The wave is not a thing, it is a description of the particular arrangements of particles.

    On the other hand there are more similarities than I thought. Reading descriptions of the double slit experiment I am often struck with the idea “real waves aren’t so orderly, they get choppy really quickly. Reading Leonard Susskind’s “Quantum Mechanic – The Theoretical Minimum” confirmed to me that the same thing happens with quantum waves.


  19. victor panzica

    There is no such thing as a rock function unless you are a geologist. Ontologically I can accept that a wave exists just like time, orbits, gravity etc. What we are really disputing is nouns vs verbs or which parts of our brains we are working with or not agreeing with.


  20. brodix


    “There is no such thing as a rock function unless you are a geologist.”

    Or a stone mason, or a paver, or a farmer, or a gardener, or a jeweler. Context.

    If that stone is part of a vertical structure, is it a wall, or a wall function? Though if you are a house builder, it would be a wall function.

    Similarly, is a wall of water molecules a wave, or a wave function? Though if you are a surfer, it is the wave function you would be most concerned with.

    It seems a bit of a forest/trees relationship.

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  21. synred

    I think ensemble interpretation is inconsistent with Field Theory. In field theory there are no particles in the usual sense. There are quantized excitations off the fields.

    That’s what we call particles. There is no wave-particle duality — all is waves/excitations. That wave goes through both slits. The waves tend to clump in ‘packets’ — this is what looks like particles to us.

    If you just turn the crank on the FT will clump and decoher and you get many worlds very naturally, but you don’t get the born rule.

    The there’s no mystery of why a ‘particle’ can be two places at once in FT. The excitation just happens to have a large amplitude at two well separated places. The mystery is how a spread out excitation comes to be in only once place. Decoherence can mae it clump in a few or many places, but how does only one surive and how does the energy in the field spread out all oer or in a couple of spots suddenly concentrate in one when a measurement occurs. ‘Many worlds’ explains this, but not the Born probability rule which is the key to the experimental success of QM. My opinon is that ‘many worlds’ advocates sweep this under the rug.

    Field theory explains the profound identy of ‘particles’, i.e., they are waves and even the Pauli exclusion rule (spin 1/2 Dirac field can only have one excitation in each state). Without Pauli we would not be here, but we don’t need weak anthropic princlple (WAP) to explain it. It isl almost a geometrical property of a spin 1/2 field. So while WAP might be needed to ‘explain’ some detailed constant choice, FT provides the basic structure of states and forces from first principle, just as albert would have liked.


  22. Alan White

    Re energy: Marc Lange has an antirealist argument about energy:

    Click to access most-famous-equation.pdf

    He and I had a vigorous correspondence about this piece many years ago–I think he’s wrong (his central argument equivocates on what a system is, but I’ve not been able to publish that), but at least it is a very interesting position worthy of serious study. FWIW.


  23. synred

    Huh? Sure there is … used to be called ‘solid state’ physics now called ‘condensed matter physics. It uses QM, and field theory. Your rock might be a metal or a crystal (like diamond).Mostly rocks are a mix. It’s properties can be computed based on what atoms they are made of and how they are arranged. Rocks and waves can be described by eqns. Being described by equations does not make them ‘unreal’
    Both rocks and waves have been around long before we figured out the equations
    You’re entering silly land here.


  24. synred


    “The wave is not a thing, it is a description of the particular arrangements of particles”

    A wave can knock you flat even if you can’t describe it. It can kill an animal with no ability to describe it. The 64 quake in Alaska was plenty real to the caribou and grizzly bears. Maybe the black flies didn’t notice it directly.

    Particles are also waves. If you want you can grant ‘ontological status’ only to the thing that is waving. In the case of light the electromagnetic field, in the case of electrons the Dirac field.

    You can grant only the medium existence but in the case of light and elementary particles will be hard pressed to detect it or being around to detect it, if it isn’t waving a good deal.

    A rock is an arrangement of particles. A person is an arrangement of particles and over time not even the same particles. At a deeper level everything is the excitation of a field and there maybe levels below that. The fields may be arrangements of ‘strings’ or ‘branes’ or some damned thing in which case the fields are not real either as they are only the arrangement and activity of, say, strings. It could be turtles all the way down. And yet here we are…

    If you don’t grant ‘ontological’ status to arrangements of things and patterns of activity, then people don’t really exist either.


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