This is a reality check type of question. I am interested in whether it's a valid distinction and whether it's been considered by others.

It occured to me the other day that the issue of 'context' or 'background' is not considered in the equations of classical physics. Newton's laws of motion apply to ideal objects with measurable attributes devoid of interference from extraneous sources (e.g. 'bodies falling in a vaccuum'.) This also explains why the laws of physics don't themselves capture or describe 'the arrow of time' as they're reversible.

By contrast, the subjects of the biological sciences can never really be considered context free, as 'the environment' is the context within which they exist. I suppose you could examine a single-celled organism microscopically and learn about its constituents, but you couldn't form any idea of what it does or how it works unless you understood its relationship to the environment in which it is found.

The question is, does this provide an argument against the efficacy of physicalism? Physicalism generally claims that 'everything is physical', however, this analysis indicates that 'the physical' is at least in classical physics a kind of idealisation, and that in real life, there are always crucial environmental and contextual factors in play which are not considered in classical physics.

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    Classical physics uses the well-known inertia frame of reference(s) as an idealized object's contextual background to define velocity of the said object, by definition one cannot detect acceleration between any two of these frames, otherwise one cannot define kinetic energy since you cannot define velocity. Also potential energy is implicitly dependent on some background object. If there's only one object in the world, there's no potential energy... Sep 18, 2023 at 23:17
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    Regarding context, in biology (specifically behavioral studies) the influence of the observer on the observed is also a consideration. Sep 19, 2023 at 2:42
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    See: this question among others at physics SE for how the laws of physics capture the arrow of time.
    – g s
    Sep 19, 2023 at 3:01
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    No, this is not a valid argument against physicalism. Newton's laws equally apply to objects interfered with by the "environment", external fields, medium, surrounding objects. It is just that in many cases a simplified model is good enough and those are neglected. Similarly, one could neglect the "environment" in biology, it is just that such models would not be useful as often. And one still has to idealize even to partially take "environment" into account. The difference is purely pragmatic and not one of principle. In ontology, one abstracts from such pragmatic considerations.
    – Conifold
    Sep 19, 2023 at 7:27
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    The sense in which physicalism relies on idealization is the same sense in which any ontology, or, indeed, any human construct, relies on idealization, reality in its fullness is beyond human grasp. Physicalists, like idealists or dualists, talk not about our idealizations but about what they point at in reality, within our limited means, and they all claim that theirs are the best pointers. Along these lines, the argument is just as much against physicalism as against everyone else. Even your own criticism of idealizations is based on idealizations, so it is self-defeating.
    – Conifold
    Sep 19, 2023 at 12:19

3 Answers 3


Physics is different from biology because it is easier in physics to isolate systems from their environment, so as to simplify their analysis. This is why the basic equations are context-independent.

However, please note the following. In the world of physics, a common simplification when dealing with high-energy particle interactions is to ignore gravity, because the effects of gravity are so extremely tiny that they do not affect the outcome of experiments we conduct in particle accelerators. The models that are built on the assumption that gravity is negligible are called background-independent because the particles do not perturb and interact with the background structure of spacetime.

However, we know that there was a time in the distant past when the energies of the particles present in the universe at that time were so huge that a proper model of their behavior must account for the gravity they generate by themselves because of their tremendous energy content. Such models are called background-dependent because those particles can and do warp spacetime, and all the attendant interactions that involve gravitational effects must be included in the physical description.

Background-dependent models are extraordinarily difficult to deal with mathematically and for this reason, no one has yet been able to write down a full set of equations describing how high-energy particles behave when the spacetime they occupy is materially affected by their presence.

To do so requires a mathematical model of what is called quantum gravity, which no one yet knows how to write.

  • Thanks but doesn't actually address the question, which is about physicalism rather than physics per se. The question is about the efficacy of physics as a general explanatory paradigm, given that it does indeed rely on an idealised model based on abstraction.
    – Wayfarer
    Sep 19, 2023 at 9:36
  • @Wayfarer If the question isn't about Physics then why is it the first word in your question "Physics"? I'm sure that is why Niels answered the way he did. I'm voting up his answer. Sep 19, 2023 at 16:11
  • well, it is a philosophy Q&A site, the question is about the application of physics to broader issues.
    – Wayfarer
    Sep 19, 2023 at 22:45

You say

"Newton's laws of motion apply to ideal objects with measurable attributes devoid of interference from extraneous sources (e.g. 'bodies falling in a vaccuum'.) This also explains why the laws of physics don't themselves capture or describe 'the arrow of time' "

You really think reconciling the thermodynamic arrow of time with spacetime would be an open problem if the answer was this simple? In mechanics you begin with elastic bodies, and idealising steps like discarding friction or ignoring other awkward but not not fundamental details, then cover inelastic scattering, coefficients of friction, etc. This is sometimes jokingly referred to as the 'spherical cow in a vacuum' approach. If your concern is with how inaccurate idealisations obscure reality from us, you should read How The Laws of Physics Lie for a thorough treatment. Idealisations and abstractions are just that, but they are gigantically effective in making things computationally tractable. It's important to question how valid they are, but ridiculous to say any abstracting is incapable of revealing more than obscuring. See more general discussion here: Is the idea of a causal chain physical (or even scientific)? You should look at the modern approach of effective field theories, for how modern physics is tying relevant theories to relevant context, eg degrees of freedom at given length and energy scales. I make the direct case that the way mathematics is less useful in biology than physics, is only a surprise because of a kind of 'physics chauvenism', which expects all explanations to come down to equations: The Unreasonable Ineffectiveness of Mathematics in most sciences So of course biology being more complex with more degrees of freedom, and involving more historucal contingency, is not an argument against physicalism, only against physics-is-all-there-is thinking that says anything not readily reducible to it is suspect.

Eliminating action-at-a-distance, was a key concern for the developing scientific picture of physicalism, removing the 'mysterious ways' of divine intervention and miracles. In this picture we have locality, and signals require movements of matter or fields restricted to light speed (entanglement partially challenges locality, but cannot be used to send information faster than light). When people want to decry physicalist-materialism I can only think this is what they take issue with, because it's the core of this very succesful approach in science. Jung's Synchronicity and Sheldrake's Morphic Resonance are examples of relatively serious attempts to question this orthodoxy.

Thermodynamically closed systems are an idealisation that is almost never totally true, and yet the only circumstance that lynchpin of modern physics the second law of thermodynamics is valid in. But again the more general case is open systems, implying context. We can work with relatively closed though, and use the second law.

Continuous symmetries under transformation, is probably the deepest area in physics, because Noether's Theorem showed they are directly equivalent to stating conaervation laws. Accounting for rotational momentum implicitly assumes the net rotation of the universe is zero, and that we can reference the restframe of the universe.

It's also assumed the net energy of the universe was likely to have been zero, with initially equal matter and antimatter (CPR symmetry violation linked to current assymetry), and a role for equal but opposite sign energy in gravitational fields to baryonic rest mass. That is, that everything began together at one time in a singularity or close to it, at the Big Bang, which seems to have had very low entropy but no mass. So context is always there. But locality means that most of the time we can discard irrelevant context when looking at particular dynamics.

I see it as wrong to describe everything as 'reducing' to physics, that instead physics is a language foe translating between contexts. Discussed here: Is the idea that "Everything is energy" even coherent?

  • thanks for the illuminating response. I'm familiar with Nancy Cartwright. But nothing you say here really detracts from the original contention - that classical physics doesn't take context into account, instead operating through laws that are said to be general and universal. They are indeed 'gigantically effective', that is not even in question, but it is what they exclude that is interesting, and that is something that has become apparent over time. Besides, if you say that physicalist reductionism is wrong, then we're in agreement on the salient point.
    – Wayfarer
    Sep 20, 2023 at 2:28
  • @Wayfarer: If you think that's what I've saud you've misread me. Abstraction is the process of sifting important signals from irrelevant. It is essential for every step of making sense of our world. Reductionism is just a mode of explanation, & we need more than that alone of course, as discussed here: 'What's the "opposite" of emergence?' philosophy.stackexchange.com/questions/81417/…
    – CriglCragl
    Sep 20, 2023 at 10:21

No, your argument is based on a misunderstanding. Physics does not overlook context. The laws of physics describe the fundamental ways in which matter interacts in spacetime. The real world context is simply the result of such interactions in aggregate. Newton's laws apply to a body falling through air just as much as they apply to a body falling through a vacuum- there are just more collisions to take into account in the former case. A practical limitation of physics is that you cannot account for all of the interactions in a typical real world setting, simply because there are too many, but that does not mean that the interactions do not obey the laws of physics. Quite the opposite, in fact. In principle you could determine the growth of a tree, say, purely through the application of the laws of physics, but the number of variables you would have to account for would be far too large for you to cope in practice.

Where physics does have limits in principle, rather than in practice, is is relation to information and meaning. Suppose your computer screen displays a sequence of numbers. The laws of physics can in principle be used to explain why each pixel on the screen is emitting a certain amount of light, but they cannot, in principle, tell you why that combination of pixels represents a string of numbers, nor what that string of numbers represents. If you are looking for arguments against physicalism, I suggest you start there.

  • 'In principle you could determine the growth of a tree, say, purely through the application of the laws of physics' - which is physicalist reductionism. But it is not at all established, the behaviour of organic molecules and the generic code is different in kind from anything described in terms of physical laws alone. With respect to your second point, I agree, I've explored a similar theme in this question philosophy.stackexchange.com/questions/98607/…
    – Wayfarer
    Sep 20, 2023 at 8:12
  • @wayfarer Why do you say that the behaviour of organic molecules cannot be determined from first principles by applying the laws of physics? Sep 20, 2023 at 8:55
  • Because molecular biologists unavoidably deal in terms that go beyond the language of physics and chemistry, invoking concepts such as “stimulus”, “response”, “signal”, “adapt”, “inherit”, and “communicate” etc, none of which have any direct counterparts in the lexicon of physics. Secondly because even the simplest organism exhibit characteristics like homeostasis and the ability to retain their form through the exchange of substances with the environment, the ability to heal, mutate, and reproduce. See royalsocietypublishing.org/doi/full/10.1098/rsta.2015.0060
    – Wayfarer
    Sep 20, 2023 at 9:57
  • But surely you can analyse stimuli, responses, etc in terms of physics. Sep 20, 2023 at 10:13
  • Likewise, the ability to heal, mutate etc. Sep 20, 2023 at 10:13

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