Classical Greek atomism arose basically as a response to the Eleatic criticism of the concept of change. The Eleatic argument was basically that if X=Y, then all properties of X must also be properties of Y, but if X is a thing at one time and Y is the same thing at a later time after the thing has changed, then X and Y don't have the same properties, so they aren't the same thing any more. Note that this is an essentialist position: X has an essential identity and it is that essential identity that cannot change.

Aristotle's solution to this problem involved distinguishing between essential and accidental properties. The atomist solution to this problem was to postulate that everything is made up of atoms, so the things of sense perception are aggregates of atoms and have no essential properties of their own. However, the atomists were still essentialists; they just pushed the essential properties down to the atoms. The atoms had essential, never-changing properties and had no parts of their own. However, this is not satisfying, because no matter how small the atoms are, you can always imagine geometrically dividing them up into parts, so the fact that they can't come apart seems more associated with the strength of the force holding them together than to a metaphysical simplicity. "Simple" means having no parts.

Does modern physicalism have the same issue? They can either appeal to subatomic particles as having no parts and having essential unchanging properties, or they can admit the existence of parts. If they think there are base particles with essential unchanging properties, then they are basically saying that science has reached its limit; there are these things in the universe that science is unable to analyze; all it can do is discover how it behaves. If they admit the existence of parts, then they are in danger of an infinite regress of parts of parts. This is a problem for physicalism because the point of physicalism is that the smaller explains the larger. You explain the behavior of a planet by explaining the behavior of the particles that make it up. If there is an infinite regress of parts, then there is no ultimate explanation of anything.

There are various evasions the physicalist can try. They can, for example, say that the basic units of the physical world are not particles but fields, but that really doesn't solve the problem. Are these fields compound objects or simple? If simple, then science has once again reached an arbitrary limit in what it can investigate. If complex, then once again there is the danger of an infinite regress.

My sense is that physicalists would not accept an infinite regress, so they seem to be committed to some layer of the universe that is metaphysically simple, that has essential properties, and that cannot be analyzed further by science.

  • I agree a final theory of physics would involve a limit beyond which there would be no further answers (why those ultimate laws and not some others), but metaphysically this needn't involve substance metaphysics and essentialism--one could also interpret the ultimate laws in terms of a structural realist metaphysics in which each particle (or other primitives, like 'events') is wholly defined by its mathematical relations to other particles/events. See Steven French's The Structure of the World or Ladyman/Ross Every Thing Must Go.
    – Hypnosifl
    Commented Sep 15, 2022 at 20:15
  • No. This analysis presupposes classical objects at the "ultimate" level, with their relation to properties and parts that is obsolete. Elementary (quantum) "particles" have no parts, but still morph into each other in collisions, so they are "simple" structurally, but not behaviorally. More particles appear at higher energy levels, so interactional behavior of any "simple" particle is potentially inexhaustible. Neither physicists no physicalists are deterred by epistemic infinite regress this entails, infinite towers of "effective" theories with no "ultimate" theory are easily envisioned
    – Conifold
    Commented Sep 15, 2022 at 21:21
  • @Conifold, I pointed out that even if you have some other notion of what particles are, then either they have parts or they don't. You suggest that they don't have parts, but they do have properties. If a thing is perfectly simple but has properties, then it must have essential properties. That is, it must have properties such that it can't be what it is without those properties, and where those properties cannot be explained by its composition and configuration. Also, the regress I was talking about is not epistemic but causal. Commented Sep 15, 2022 at 23:42
  • Sure, quantum particles have properties, we can even call some essential. But they are not unchanging, electrons get annihilated by positrons with photons emitted, and those are equally "simple". Your examples of "smaller explains larger" are all classical mechanistic ones, physics abandoned this mode of explanation since the fall of aether. Why is "analyzing" supposed to be breaking up into parts rather than modeling morphing behavior? How is discovering "smaller parts" saliently different from discovering "how it behaves" when refining models? And how does explanatory regress become causal?
    – Conifold
    Commented Sep 16, 2022 at 1:07
  • 1
    I'm having difficulty seeing what’s essential in inflationary multiverse theories, where entire universes can be devoid of particles or similar degenerate cases. Another problem is that these multiverses are sometimes brought in to explain things, such as Susskind does to argue why we don’t observe Boltzmann brains. Hardly simples doing the explanatory or causal legwork. Maybe there's one multiverse wide field, but you need to sum over the entire multiverse to explain some things, like why BB's are rare, why time only goes forward, like here youtu.be/jhnKBKZvb_U?t=2940 (Susskind)
    – J Kusin
    Commented Sep 16, 2022 at 16:11

1 Answer 1


This question has some understandable confusion between science and physicalism, and also about what relation essentialism has to science.

Science is based on the principle that our world is contingent, and discovering its features requires investigation, rather than reasoning. Whether that investigation will ever terminate, is left as a TBD by science. Note, there are three possible resolutions of Munchausens's Trilemma, and circularity is a third alternative to your infinite regress and unexplained brute fact. If elementary particles are unexplained -- IE we never discover a reason for the features of Standard Model of Quantum Mechanics, or for the non-integrated Theory of General Relativity -- that may be a possible termination of physics.

Note, science in general has adopted emergent pluralism as its primary ontologic view of itself. See section 5 of the SEP on scientific reduction: https://plato.stanford.edu/entries/scientific-reduction/ This pluralism extends to non-science as well, where the consensus view in and outside science, is that scientism's clam that science is the only valid source of knowledge about the world, is overwhelmingly false.

Physicalism is not an essentialist view. It has been adopted as a next best alternative by the materialists when the essentialist "materialism" of the 19th century was refuted by modern physics showing that "matter" wasn't fundamental to physics. Despite its widespread adoption within the philosophic community, physicalists themselves have had a great deal of difficulty even characterizing what physicalism IS.

This is because when originally adopted, physicalism presumed scientism, and scientific reductionism. With the widespread rejection of both premises, physicalism has come somewhat unmoored as a worldview. Hempel's Dilemma highlights this -- Hempel noted one cannot define physics or physicalism in a way that has testable (Popperian) content, and excludes the things that physicalists want to exclude (causal consciousness), and is not false.

Here are four good recent references on physicalism that exemplify its current problems. The links go to my reviews for the first 3. https://www.amazon.com/gp/customer-reviews/R13R2OUNXMIN6H/ref=cm_cr_dp_d_rvw_ttl?ie=UTF8&ASIN=0415452635, https://www.amazon.com/gp/customer-reviews/R1LFTMUSP8VEWB/ref=cm_cr_dp_d_rvw_ttl?ie=UTF8&ASIN=0691113750, https://www.amazon.com/gp/customer-reviews/R1A8I0RTYJEDJM/ref=cm_cr_dp_d_rvw_ttl?ie=UTF8&ASIN=0521827116, https://www.academia.edu/819823/The_Rise_of_Physicalism

Note that of the four authors, two abandoned physicalism as a result of their exploration of the subject, and all four accept the reality of abstract objects (IE reject that everything is physical).

Physicalists today, unlike the first three authors, primarily are emergent physicalists. They accept pluralism in science and the universe, so believe that emergent phenomena are "real". Where emergent physicalists diverge from pluralism, is they hold that somehow physics is MORE real than any other subject area. How one arrives at this conclusion epistemologically -- is unclear to me. Science operates on indirect realism, where well supported hypotheses are presumed to be real, and there is no mechanism in this method for a more vs less "real".

A further presumption of physicalism is causal closure of physics. This is an assumption -- that when science is done characterizing the world, that there will be no causation needed from any emergent or pluralist phenomena -- IE explicitly from abstract objects, or from consciousness (or from anything spiritual, if science discovers the spiritual) -- onto physics. Note, this causal closure assumption -- is SPECULATION, and is actually in conflict with strong emergence, and with non-science pluralism, and with the recent inclinations of theoretical physicists, many of whom consider math to be causal of physics.

Repeating the answer to your question --while these physicalist assumptions may be questionable, they are not ESSENTIALISM.

  • I really appreciate an up to date rendering of physicalism. The SEP page on it completely abdicates on defining it. +1
    – J Kusin
    Commented Sep 16, 2022 at 16:20
  • Very useful and informative, thank you. I didn't know that many physicalists had given up on scientific reductionism; my question was about the physicalism that does assume scientific reductionism (maybe the question should have been about scientific reductionism instead of physicalism). In that form, my question is still unanswered: "they seem to be committed to some layer of the universe that is metaphysically simple, that has essential properties, and that cannot be analyzed further by science". Is that correct or am I missing something? Commented Sep 16, 2022 at 17:13
  • 2
    "Note, science in general has adopted emergent pluralism as its primary ontologic view of itself." Do you mean that philosophers have mostly adopted this view? Nearly every prominent natural scientists I've seen commenting on reductionism, whether in physics or biology, has endorsed the basic idea that all physical behavior is likely to be in principle derivable from physics alone, even if they don't endorse other forms of reductionism like methodological reductionism or ontological reductionism.
    – Hypnosifl
    Commented Sep 16, 2022 at 18:33
  • @Hypnosifl -- The SEP article was describing the views of philosophers of science. For scientists themselves -- you say you know biologists and physicists? Physicists may like the idea that they are the only science that studies "real" reality, but in my experience, most other scientists consider physicists to be a bit too full of themselves, and a inappropriately dismissive of the independence of the other sciences. For biologists, do you know NON-biochemists? Biochemistry is the only sub-field of any science other than chemistry where reductionism has had much success.
    – Dcleve
    Commented Sep 17, 2022 at 12:37
  • @Hypnosifl -- Further, do the biologists you know happen to be Neuroscientists? Neuroscience is the only field of science I know of today where total reductionism is still the dominant worldview. This is a bit of a historical anomaly, as Francis Crick, a devoted eliminative reductionist, successfully set out to recruit a generation of Neuroscientists with a similar mindset. The Wiki article on neuroscience notes, however, that in the most recent decade, NON-reductionist approaches have finally entered neuroscience as well, likely due to the failures there for pure reduction.
    – Dcleve
    Commented Sep 17, 2022 at 12:46

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