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Ilya Prigogine & Isabelle Stengers “Dynamics from Leibniz to Lucretius”

Prigogine, Ilya; Isabelle Stengers 1982. Postface: Dynamics from Leibniz to Lucretius. – Serres, Michel. Hermes: Literature, Science, Philosophy. Baltimore; London: The Johns Hopkins University Press, 135-158

Newtonian  physics  posits  a  body  assumed  to  be  isolated, endowed with a rectilinear and uniform inertial movement, and calculates the modifications of this movement as determined by the action of forces. For Leibniz,  the forces  are  not “given”  and  are  in no way  the real  causes of the  modification  of a  movement  but rather are  local properties within a  dynamic  system:  at  every  point,  they  characterize  a  momentary  state belonging to a series regulated  by a law. (141)

The  optimal point of view on  a system,  the  best  choice  of variables,  is therefore the one that cancels out the potential energy redefined in terms of  these  variables.  And  dynamic  theory  tells  us  that  every  integrable system  can  be  represented  in  this  way -can  be  redefined  as  a  set  of “units”  evolving in  a  pseudo-inertial  movement,  without any interaction among the “units.” Each “monadic unit” is no longer determined in each of its movements by interactions with the aggregate ; each deploys its own law for  itself,  alone  in  a system  which  it reflects intrinsically, because  its very definition supposes and translates this system in every detail. There is full passage between the local  and  the  global. (144)

Quantum mechanics thus presents a reversal of perspective relative to classical  style.  It  is  no  longer  a  question  of looking  for  simplicity  at  the level  of  elementary  behavior.  Dynamic  simplicity,  as  reflected  by  the possibility  of  a  completely  monadic  represen tation,  belongs,  in  fact,  to the macroscopic world, to  the world on our scale. Our  physics is a science created by macroscopic  beings,  created  with conceptual  tools and instruments  that  belong  to  the  macroscopic  world.  It  is  from  that  position, when  we  question  the  world  of  quanta,  that  we  must  choose  what  will allow  us  to  express  matters  in  terms  of  measurable,  reproducible,  and communicable properties. We can no  longer allow ourselves, as far as the physical  world  is  concerned ,  the  privileged  point  of  view  which,  when pushed  to  its limit, we once could  have iden tified as that of God. (147)

We  can  see  how unfortunate  was the widespread assumption that quantum mechanics “discovered”  that the process of measurement disturbs the system nwasured. Uncontrollably modifying; the values of certain parameters in order to ascertain the value of others. Such an assumption in fact implies that only an arbitrary positivistic prohibition pn’vt’nts us from speaking; of “hidden variables,” that is to say, pr(‘vents us from affirming; that the system  in question is, at every moment, defilwd by tht, St’t of physical parameters, even if all of them cannot be known simultaneously. The actual situation is entirely different. The real discovery of quantum mechanics, as it is expressed by the inseparable character of reversible (‘volution and irreversible reduction, is not that tht, process of measurement disturbs, but rather that it participates in the definition of, the measured parameter, so that this parameter cannot be attributed to the quantum system “in itself” and one cannot speak of “hidden variables.” As Niels Bohr repeatedly said, quantum  mechanics  discovered  the  necessity of choic(‘, choosing; what question to ask,  in other  words, choosing; both  the  instrumental  framework  of the  question  and one of the complementary descriptions articulated among; themselves by formalism but irreducible to a single description. (147 – footnote)

“The world as it is is not the product of my  representation ;  my  knowledge,  on  the  contrary,  is a  product  of the world  in  the  process  of becoming.  Things  themselves  choose,  exclude, meet, and give rise to one  another.” (151 – Serres „Hermes IV“, 157-158)

An  unstable  system,  on  the  other  hand,  is  a  system  in  which  the initial  conditions  determining  various  qualitatively  distinct  behaviors are not  clearly  separated  but are,  on  the  contrary,  as close  as one  might wish. We are all familiar with this sort of intimate mixture -it is described by  number  theory: every  rational  number  is  surrounded  by  irrationals, and every irrational by rationals. Similarly, whatever the neighborhood defined for an  initial  state, one always finds at least one other state giving rise  to  a  qualitatively different behavior,  just as  oscillation  and rotation are qualitatively different. (151)

Under  these  conditions,  in  order  to  predict  deterministically  the  type of behavior  the  system  will  adopt,  one  would  need  infinite precision.  It is of no use  to  increase  the  level  of precision  or even to make  it tend toward infinity;  uncertainty  always  remains  complete -it  does  not  diminish  as precision  increases.  That  means  that  divine  knowledge  is  no  longer implied in human knowledge as its limit,  as that toward which one might tend with increasing precision ; it is something other, separated by a gap. (152)

It is not  a  question  of recognizing  that we  are  incapable  of calculating  such  traj ectories;  rather,  it is  a  question of  realizing  that  the  trajectory  is  not  an  adequate  physical  concept  for these  systems.  Henceforth  the  field  of  dynamics  will  appear  larger systems  described  in  terms  of  trajectories  with  their  determinist  and reversible properties are only a particular class within that field. (152)

Creative  chaos is illegality itself, for its description dissolves the distinction between the macroscopic state  and  the microscopic fluctuation ; correlations can appear among distant events; local deviations echo throughout the  system -the matrix-state  in  which  fluctuations are  amplified and from  which things  are born. (153-154)

And  thus  Serres  is  correct:  the question  is  reversed.  It  is  no  longer necessary to ask where the clinamen comes from or how one might justify the  disturbing  of  laws.  All  laminar  flows  can  become  unstable  past  a certain  threshold of velocity,  and  that  was  known  just as  the  productive nature  of  organized  forms,  of  bifurcating  evolution,  of  what  we  call dissipative  structures,  was  known.  One  must  ask  how  an  abstraction  of this  knowledge  could  have  been  made  to  describe  the  world  in  order, subject to a universal law. We already know one answer given by Serres. Classical science is a science of engineers who knew, of course, that their flows were never perfectly laminar, but who made  the theory of laminar flow perfectly controllable and directable, the only flow for which knowing is controlling. (154)

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