Transcript Physics and the `Real Patterns` theory of ontology

Physics and the ‘Real Patterns’
theory of ontology’
James Ladyman
Thanks to Joss and Richard
and the Lorentz Centre
• The document that describes the topic of the
conference does a great job of identifying a
lot of important and fascinating issues.
• Thanks to the physicists for informing us
about the relevant phenomena.
• My ideas owe a lot to my co-authors Steven
French and Don Ross.
• The material on phlogiston is forthcoming in a
paper in Synthese
Three Ideas
1. Structure is retained on theory change even
when ontology is not.
2. Structuralism about a domain involves the
idea that the entities in the domain are
mutually dependent on each other for their
existence/individuation.
3. Real Patterns
– In the case of physical structures I contend that
these three ideas all centrally involve modality.
Of what is everything made?
• Western philosophy allegedly started when
the pre-Socratics asked this question.
• This is a metaphysical question physics is
supposed to answer.
• It presupposes that the world comes in a
hierarchy of levels and that there is a
fundamental level with a few basic kinds of
entities.
• The most naïve picture is one of physical
objects ordered by (spatial) size and
ultimately composed of elementary particles.
Levels
• There is not necessarily a single hierarchy
• Ordering by spatiotemporal scale
• Ordering by energy
• Ordering by composition
• Anomalous sciences: evolution, game theory,
economics, thermodynamics,
Scepticism about Levels
• Spatiotemporal scale may not be a fundamental feature of
reality. It is an open question whether quantum gravity will take
the spatiotemporal manifold as primitive rather than emergence.
• The same may be true of the energy scale.
• The levels structure based on the composition relation is
undermined by the fact that the notion of composition does not
translate well into physics:
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Of what are quasiparticles composed?
Are particles composed of quantum fields?
What composes a black hole?
1. Theory Change as a
Motivation for Structuralism
• Antirealism: science saves the phenomena
• Realism: science describes the furniture of
the world
• Structural Realism: science tells us about the
structure of the world - more than merely
saving the phenomena but less than full
ontological commitment
– Example: even the existence of central theoretical
entities is necessary for more than empirical
adequacy.
The Theory of Phlogiston
• Burning is a process in which a principle of
combustion is given off by the fuel and enters
the air.
The Theory of Phlogiston
• Burning is a process in which a principle of
combustion is given off by the fuel and enters the air.
• All flammable substances are supposed to contain
phlogiston and it is what all metals have in common.
The Theory of Phlogiston
• Burning is a process in which a principle of
combustion is given off by the fuel and enters the air.
• All flammable substances are supposed to contain
phlogiston and it is what all metals have in common.
• There is no such substance and ordinary combustion
is the addition of oxygen to something and not the
emission of something by the fuel.
The Theory of Phlogiston
• Burning is a process in which a principle of combustion is given
off by the fuel and enters the air.
• All flammable substances are supposed to contain phlogiston
and it is what all metals have in common.
• There is no such substance and ordinary combustion is the
addition of oxygen to something and not the emission of
something by the fuel.
• So it seems obvious that phlogiston theory must be bad science.
The Theory of Phlogiston (heyday 1700-1790)
• Becher (1635-1682) proposed combustible earth (as one of
three earths composing ordinary substances).
The Theory of Phlogiston (heyday 1700-1790)
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Becher (1635-1682) proposed combustible earth (as one of three
earths composing ordinary substances).
Stahl (1660-1734) proposed phlogiston in 1697 (also year the world’s
first heat engine was built): parallels between metals heated in air
(calcination) and ordinary combustion – creation of dust and light often
given off, lots of air needed. Phlogiston given off in combustion - flames
The Theory of Phlogiston (heyday 1700-1790)
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Becher (1635-1682) proposed combustible earth (as one of three
earths composing ordinary substances).
Stahl (1660-1734) proposed phlogiston in 1697 (also year the world’s
first heat engine was built): parallels between metals heated in air
(calcination) and ordinary combustion – creation of dust and light often
given off, lots of air needed. Phlogiston given off in combustion - flames
Wood turns to ash when burnt (phlogiston must therefore have mass).
Iron rusts to calx also giving off phlogiston.
Charcoal combusts almost completely so charcoal is very nearly pure
phlogiston.
The Theory of Phlogiston (heyday 1700-1790)
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Becher (1635-1682) proposed combustible earth (as one of three
earths composing ordinary substances).
Stahl (1660-1734) proposed phlogiston in 1697 (also year the world’s
first heat engine was built): parallels between metals heated in air
(calcination) and ordinary combustion – creation of dust and light often
given off, lots of air needed. Phlogiston given off in combustion - flames
Wood turns to ash when burnt (phlogiston must therefore have mass).
Iron rusts to calx also giving off phlogiston.
Charcoal combusts almost completely so charcoal is very nearly pure
phlogiston.
Phlogiston was supposed to have a metallic quality. Metal calx burnt in
charcoal becomes ordinary metal - adding phlogiston adds the metallic
quality to the true form (calx) of the metal (practical application to
copper mining).
The Theory of Phlogiston (heyday 1700-1790)
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Becher (1635-1682) proposed combustible earth (as one of three earths
composing ordinary substances).
Stahl (1660-1734) proposed phlogiston in 1697 (also year the world’s first heat
engine was built): parallels between metals heated in air (calcination) and
ordinary combustion – creation of dust and light often given off, lots of air
needed. Phlogiston given off in combustion - flames
Wood turns to ash when burnt (phlogiston must therefore have mass).
Iron rusts to calx also giving off phlogiston.
Charcoal combusts almost completely so charcoal is very nearly pure
phlogiston.
Phlogiston was supposed to have a metallic quality. Metal calx burnt in charcoal
becomes ordinary metal - adding phlogiston adds the metallic quality to the true
form (calx) of the metal (practical application to copper mining).
When something burns in a sealed container it uses up the oxygen in the air
until eventually the fire goes out. This was explained in terms of the saturation of
the air with phlogiston.
Combustion, respiration and calcification are all the same kind of reaction
(oxidisation). (Animals in a sealed chamber phlogisticate the air (Boyle).)
The Theory of Phlogiston
Big Problem
• Since Rey (1630) it was known that the calx of a metal could be
heavier than its metallic form.
• Some Stahlians posited negative weight for metallic phlogiston
but most believed that impurities caused the weight increase.
Priestley (1733-1804)
• Plants dephlogisticate the air (cycle between plants
and animals).
• Air without any phlogiston is air whose potential to be
burnt is maximal.
• Dephlogisticated air by heating a calx (red mercury)
(1774)
• Scheele (1742-1786): ‘fire air’ (1771-2, published
1777)
• There is a clear sense in which the dephlogisticated
air that Priestley describes breathing is oxygen.
Priestley (1733-1804)
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Plants dephlogisticate the air (cycle between plants and animals).
Air without any phlogiston is air whose potential to be burnt is maximal.
Dephlogisticated air by heating a calx (red mercury) (Priestley 1774)
Scheele (1742-1786): ‘fire air’ (1771-2, published 1777)
There is a clear sense in which the dephlogisticated air that Priestley
describes breathing is oxygen.
Phlogisticated air is air saturated with phlogiston.
Inflammable air [hydrogen (Cavendish 1766)] is pure phlogiston not
charcoal according to Cavendish.
Priestley burned metal oxide in inflammable air to make pure metal
(and water) - reduction inverse of oxidisation.
But inflammable air is obviously not just ordinary air with phlogiston in
higher concentration, since ordinary air becomes saturated with
phlogiston during combustion and eventually the fire goes out.
Some of the phlogisticated air dissolves in water (carbon dioxide) and
some does not (mostly nitrogen). Neither supports ordinary combustion
(like Oxygen) or reduction (like hydrogen).
Lavoiser (1743-1794)
• Oxygen (dephlogisticated air) and hydrogen
(phlogisticated air) found in compound ordinary air
and make up water.
• Burning, respiration and rusting of iron are all
oxidisation.
• But he also thought all acids contain oxygen and that
oxygen was a principle not an element.
Realists on Phlogiston
• Among philosophers ‘phlogiston’ is a prime example
of a non-referring theoretical term.
“phlogiston refers to nothing” (Psillos)
‘Phlogiston’ is a counterexample to the simple causal
theory since then it would refer to oxygen (whatever
is involved in combustion) (Bird)
Phlogiston’s Success
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Explains loss of weight of wood, coal and ordinary substance when burnt.
Charcoal leaves hardly any ash because it is almost pure phlogiston.
Air saturated with phlogiston cannot support respiration.
Metal + heat (in air) = calx [metal oxide] + phlogisticated air [de-oxygenated air]
Calx + charcoal (source of phlogiston) = metal (+ fixed air [carbon dioxide (Joseph Black
(1728-1799) 1754)])
So Metal = calx + phlogiston (explaining what metals have in common)
Charcoal = calx (fixed air) + phlogiston
Metal + acid = salt + inflammable air (note Lavoisier thought acids had to contain oxygen)
Metal + water = calx + inflammable air
(Water = inflammable air [hydrogen] + dephlogisticated air [oxygen])
Dephlogisticated marine acid (Scheele) = chlorine (Davy).
novel prediction: heat calx in inflammable air to get pure metal
novel prediction of new acids by Scheele (formic acid, lactic acid)
Animals and plants have opposite effects on the air - the former phlogisticate and the latter
dephlogisticate
Metals are alike (lost by intermediary science between Priestley and electronic chemistry).
Phlogistication and dephlogistication are inverse chemical reactions (reduction and
oxygenation)
• ‘phlogistication’ and ‘dephlogistication’ can be
regarded as referring to the processes of
oxidation and reduction, where these are
understood in the general sense of the
formation of an ionic bond with an
electronegative substance, and the regaining
of electrons respectively.
• ‘phlogistication’ and ‘dephlogistication’ can be
regarded as referring to the processes of oxidation
and reduction, where these are understood in the
general sense of the formation of an ionic bond with
an electronegative substance, and the regaining of
electrons respectively.
• If the oxidising agent is oxygen, and the oxidised
compound is a source of carbon then the product is
carbon dioxide i.e. fixed air. (combustion of fossil
fuels)
• If the oxidising agent is an acid, then hydrogen is
emitted.
• ‘phlogistication’ and ‘dephlogistication’ can be
regarded as referring to the processes of oxidation
and reduction, where these are understood in the
general sense of the formation of an ionic bond with
an electronegative substance, and the regaining of
electrons respectively.
• If the oxidising agent is oxygen, and the oxidised
compound is a source of carbon then the product is
carbon dioxide i.e. fixed air. If the oxidising agent is
an acid, then hydrogen is emitted.
• We could go further and allow that ‘phlogiston rich’
and ‘phlogiston deficient’ refer too, namely to strongly
electro-negative and electro-positive molecules
respectively.
• One could even argue that ‘phlogiston’ refers to
electrons in the outer orbital of an atom.
Forgotten Wisdom: Whewell, History of
the Inductive Sciences
• “But we must not forget how natural it was to
suppose that some part of a body was
destroyed or removed by combustion…It
would be easy to show, from the writings of
phlogistic chemists, what important and
extensive truths their theory enabled them to
express simply and clearly.”
• Combustion, respiration and calcination of
metals are all the same kind of reaction and
there is an inverse kind of reaction too.
Structural Realism
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John Worrall (1989) introduced structural realism (although he
attributes its original formulation to Poincaré). Using the case of the
transition in nineteenth century optics from Fresnel's elastic solid ether
theory to Maxwell's theory of the electromagnetic field, Worrall argues
that:
“There was an important element of continuity in the shift from Fresnel
to Maxwell – and this was much more than a simple question of
carrying over the successful empirical content into the new theory. At
the same time it was rather less than a carrying over of the full
theoretical content or full theoretical mechanisms (even in approximate
form) ... There was continuity or accumulation in the shift, but the
continuity is one of form or structure, not of content (1989, 117).
More Structural Realism
• Instructive historical examples:
 The transition from Fresnel’s ether theory of light to Maxwell’s
electromagnetic field theory.
 The transition from Galilean relativity to Lorentz invariance.
 The transition from classical mechanics to quantum mechanics.
 The transition from Newtonian gravitation to General Relativity.
Modality
• We have been very focused on the
composition of wholes by parts and have not
addressed the key issue of the status of
putative causal claims at different levels.
• More generally, I consider modality to be a
central issue for the philosophy of physics.
(Counterfactual definiteness + Locality is
sufficient to prove Bell’s theorem (cf. Tomasz
Bigaj in SHPMP).)
Modality
• Realism: physics tells us about
causation, the laws of nature and deep
metaphysics
• Antirealism: physics gives maximally
general descriptions of regularities in
the phenomena
Modality
• Realism: physics tells us about causation, the
laws of nature and deep metaphysics
• Antirealism: physics gives maximally general
descriptions of regularities in the phenomena
o Example: the speed limit of light speed - is it merely a
generalization that is true or does it have some kind
of necessary status?
Modality
• Realism: physics tells us about causation, the
laws of nature and deep metaphysics
• Antirealism: physics gives maximally general
descriptions of regularities in the phenomena
o Example: the speed limit of light speed - is it merely a
generalization that is true or does it have some kind
of necessary status?
o Example: the laws and the constants and the finetuning argument
Is Physics Special and is
fundamental physics special with
respect to the rest of physics?
“In science there is only physics; all the rest is
stamp collecting.”
Ernest Rutherford
The Incompleteness of the
Special Sciences
• In all the special sciences it is acceptable to
invoke entities and processes from more
fundamental sciences in explanations.
• For example, the economy may be affected
by the weather, living systems may be
affected by radiation, chemical reactions may
be affected by magnetic fields, and so on.
• There is a fundamental asymmetry between
physics and the special sciences.
The Completeness of Physics
• Fundamental physics aspires to a kind of
completeness in so far as it is never permitted
to invoke entities or processes from the
special sciences in an explanation of the
behaviour of the the fundamentally physical.
• Physics is analytically complete since it is the
only science that cannot be left incomplete.
Fundamental Physics
• Measurements at all scales and at all
locations in spacetime are potential
falsifications or confirmations of fundamental
physics.
• This is not true of any other science.
• Fundamental physics may not exist other
than as a limiting ideal (if there is no
fundamental level).
• (Many parts of physics are special sciences.)
The Primacy of Physics Constraint (PPC)
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Naturalists ought only to accept a form of physicalism that is motivated
by reflection on the history of science and the nature and practice of
contemporary science. Ladyman and Ross argue that this justifies
nothing more than the PPC (methodological physicalism):
“Special science hypotheses that conflict with fundamental physics, or
such consensus as there is in fundamental physics, should be rejected
for that reason alone. Fundamental physical hypotheses are not
symmetrically hostage to the conclusions of the special sciences.”
(2007, 44)
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This leaves it open to the naturalist to believe both that the entities
posited by the special sciences exist, and that the causal relations
posited by them are genuine.
2. Structuralism and the PartWhole relation
• The natural numbers are often said to
ontologically depend on each other and the
relations among them - so the parts depend
on the whole.
• Cf. the identity and individuality of spacetime
points depends on the metric field and hence
again the parts depend on the whole.
• Structuralism: less than ontological
commitment to the dressing theory is
given; more than relations among the
phenomena.
Objects and Individuals
• What does it take to be an object?
• What does it take to be an individual?
• Quasi-particles, Bose Einstein Condensates, Cooper
pairs, entangled photon pairs, quantum fields…
• Do they ‘exist’ in the same sense as tables and
chairs?
Individuation
• PII and weak discernibility - structures
admitting a non-trivial automorphism complex plane, fermions in the singlet
state (Michal)
• purely relational individuation
• an asymmetric graph of order 6: pure
relations can give rise to absolute
discernibility
Quasi-Particles
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Bipolaron
Chargon
Configuron
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Electron hole
Exciton
Fracton
Holon
Libron
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Magnon
Phason
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Phonon
Plasmon
Polaron
Polariton
Roton
Soliton
Spinon
a bound pair of two polarons
a quasiparticle produced as a result of electron spin-charge separation
an elementary configurational excitation in an amorphous material which
involves breaking of a chemical bond
a lack of electron in a valence band
a bound state of an electron and a hole
a collective quantized vibration on a substrate with a fractal structure.
a quasi-particle resulting as a result of electron spin-charge separation
a quasiparticle associated with the librational motion of molecules in a
molecular crystal
a coherent excitation of electron spins in a material
vibrational modes in a quasicrystal associated with atomic
rearrangements
vibrational modes in a crystal lattice associated with atomic shifts
a coherent excitation of a plasma
a moving charged quasiparticle that is surrounded by ions in a material
a mixture of photon with other quasiparticles
elementary excitation in superfluid Helium-4
a self-reinforcing solitary excitation wave
a quasiparticle produced as a result of electron spin-charge separation
3. Real Patterns
• macroscopic objects as relatively stable
and enduring patterns that emerge
within the structure of the quantum state
of the world.
• On such a view, the world need not form
a compositional hierarchy, with or
without ultimate parts.
Special Science Ontology
• In science one is only interested in recovering the statistical
properties of low-level entities when tracking high level ones.
• Coarse-graining and approximation are necessary for special
science ontologies to emerge. This explains why even token
identities do not obtain between say a cat and its constituent
atoms.
• In the special sciences one is usually interested in ‘universal’
forms of behaviour, where ‘universal’ means independent of
microphysical or lower level constitution. The identification of
universality and the appropriate descriptive categories for
tracking it is one of the principle tasks of the special sciences.
• The scale relativity of ontology (Ladyman and Ross)
• The renormalization group view of the world (Sokal and
Bricmont): the renormalization group describes transformations
that allow the number of degrees of freedom in the Hamiltonian
of a system to be massively reduced while still recovering the
critical behaviour of the system.
Complexity
• The special sciences are possible because the world is to some
extent algorithmically compressible. At certain levels of
description it is possible to use much less information to predict
the behaviour of systems described in an approximate and
probabilistic way, than would be needed to describe their
microstates.
• For example, Kepler’s laws, the ideal gas laws, the Hardy–
Weinberg law,… In fact all laws in the special sciences are like
this. The special sciences rely upon reduction in the degrees of
freedom of the system.
• There are real patterns in the world that are only visible at the
right scales of resolution and degrees of approximation. If you
don’t see them you are missing something about reality and that
is good enough to allow us to say that the objects, properties
and processes described by the special sciences are real.
Computational Approaches to
Emergence
• between order and randomness
• logical depth, thermodynamic depth,
statistical complexity, information
theoretic entropy, algorithmic
complexity,…
• complex systems involve hierarchical
organisation.
Real Patterns
• Daniel Dennett’s notion of ‘real pattern’ is a
computational one.
• The idea is based on the compression of data and
the reduction of information processing made
possible by a high level description of a system that
could in principle be described at a fine-grained level
but at a much greater computational cost.
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John Conway’s ‘Game of Life’ is based on a simple implementation of
cellular automata that makes a particular range of stable dynamic
attractors highly salient to people.
A person using the system naturally book-keeps its state sequences by
reference to a typology of ‘emergent’ objects—‘gliders’, ‘eaters’,
‘spaceships’, etc.—that have only virtual persistence. (That is, two
successive instances of ‘the same’ glider share only structure, and
common participation in structures larger than themselves.
A glider is clearly mereologically composed of a small number of
illuminated cells. However, its successive instances are composed of
different cells, and successive instances a few steps apart have no
cells in common.)
Once this descriptive stance is adopted towards Life, almost all users
spontaneously track the dynamics in terms of causal interactions
among instances of these types—for example, a glider will be caused
to disappear through interacting with an eater. That is, Life users
naturally begin logging causal generalizations about the types of virtual
objects, and thereby seem to commit themselves to their objective
existence.
(All the above paragraphs are taken from Ladyman and Ross (2007), chapter 4.)
– One should be cautious in using the Game of Life as a
metaphysical model of the universe.
– It is useful for the purposes to which Dennett puts it,
because it shows how patterns can emerge at grains of
analysis coarser than the grain at which what is analogous to
the fundamental microphysical level is studied, even when
all causal processes governing the latter are non-complex,
known, measurable, and deterministic. Life is thus a good
antidote to romantic interpretations of emergence.
– However, because in Life there is an unambiguous
fundamental level composed of the aggregation of a finite
number of little things, and because no higher-level object
types cross-classify the dimensions of any models of the
game relative to classifications in terms of cells, Life differs
greatly from the universe with respect to the kinds of
reductionism sustainable in it. Life admits of complete
decomposition; the universe might not.
(All the above paragraphs are taken from Ladyman and Ross (2007), chapter 4.)
Definition of Real Patterns
(Ladyman and Ross, 2007, chapter 3
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II.
To be is to be a real pattern; and a pattern is real iff
it is projectible under at least one physically possible
perspective; and,
it encodes information about at least one structure of events
or entities S where that encoding is more efficient, in
information-theoretic terms, than the bit-map encoding of S,
and where for at least one of the physically possible
perspectives under which the pattern is projectible, there
exists an aspect of S that cannot be tracked unless the
encoding is recovered from the perspective in question.
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According to RP, the utility of the intentional stance is a special case of
the utility of scale-relative perspectives in general in science, and
expresses a fact about the way in which reality is organized—that is to
say, a metaphysical fact. The fact in question is what we (but not
Dennett) call the scale relativity of ontology.
Scale relativity of epistemology isn’t controversial. To borrow an
example from Wallace (2001), if you want to predict what a hungry tiger
will do when confronted with a deer, you should study whole
behavioural patterns of whole tigers, not individual tiger cells or
molecules. It is clearly motivated by any thesis to the effect that models
of complex systems are scientifically useful.
(All the above paragraphs are taken from Ladyman and Ross (2007), chapter 4.)
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trade offs between scope, accuracy and simplicity
• Real patterns are preserved on theory
change - cf. Butterfield on the Krebs
cycle.
• Dennett’s paper is notoriously unclear
about whether ‘real patterns’ should be
regarded as real or as useful fictions.
• realism versus pragmatism metaphysics versus epistemology
• Conservative metaphysicians would complain, the eater is a
redundant causal factor, since the program underlying Life,
which in its declarative representation quantifies only over cells,
is strictly deterministic. We are reminded that an eater or a glider
is, at any given time, ‘made of’ cells and nothing else. Then we
are invited to agree that a thing cannot have causal efficacy over
and above the summed causal capacities of the parts with which
it is allegedly identical. The result is supposed to be
reductionism, and instrumentalism about gliders and eaters.
(The above paragraph is from Ladyman and Ross (2007), chapter 4.)
• Real patterns are defined modally.
• They are there to be discovered.
• David Wallace advocates what he calls a functionalist
account of ontology based on the notion of real
patterns in his elucidation of the Everettian
interpretation of quantum mechanics.
• His ontology is two-tier in that only higher-order
entities such as cats and tables are understood in
terms of real patterns, whereas the wavefunction or
whatever else proves to be fundamental in physics is
understood in categorical rather than functional
terms.
• On the other hand, James Ladyman and Don
Ross (2007) advocate a real patterns account
of ontology across the board.
• All real patterns are real but there is an
asymmetric relation among them.
• The relation is not composition since
emergent structure is not reducible to the
sum of the parts - no building blocks (Healey)
• Real patterns theory can be developed in
terms of the dynamics of phase spaces rather
than in computational terms. (Jenann Ismael
suggested this.)
• Reducing the number of degrees of freedom
by finding ‘objects’.
• There are synchronic patterns too of course
but they could be represented in terms of
laws of co-existence.