O slideshow foi denunciado.
Utilizamos seu perfil e dados de atividades no LinkedIn para personalizar e exibir anúncios mais relevantes. Altere suas preferências de anúncios quando desejar.

Purpose and the Universe

64.978 visualizações

Publicada em

Keynote address at the 2013 American Humanist Association conference.

Publicada em: Tecnologia, Educação

Purpose and the Universe

  1. 1. purposeand the universeSean CarrollCaltechpreposterousuniverse.com
  2. 2. Lucia de BerkDutch nurse convicted in 2004 forthe murder of 7 infant children andattempted murder of 3 more.Sentenced to life in prison.Expert witness: chance of one nursebeing on duty for all the incidentsis 1 in 342 million.Re-analysis: actually it was 1 in 26.Exonerated by re-trial in 2010.
  3. 3. Pat Robertson after Haiti earthquake:“Many years ago, the island’s people‘swore a pact to the devil.’ True story.And so the devil said, ‘OK, it’s a deal.’They kicked the French out. TheHaitians revolted and got themselves free.Ever since, they have been cursed by onething after the other.”The urge to find reasonsPrinciple of Sufficient Reason(Spinoza 1663, Leibniz 1686):“Nothing is without a groundor reason why it is.”
  4. 4. The Ethos of ScienceWe do not get to place demands on the universe.We cannot discover how things work by pure thought.What we want to be true doesn’t matter.We gain understanding by considering everypossible way things could be, testing them againstobservation and experiment, and deciding whatbest accounts for the data.
  5. 5. Purpose from a Designer (God)Why did God make us? God made us to showforth His goodness and to share with us Hiseverlasting happiness in heaven.- The Baltimore CatechismIt’s not about you… You were born by[God’s] purpose and for his purpose.- Rick Warren, The Purpose Driven LifeThat which has come into existence mustnecessarily, as we say, have come intoexistence by reason of some Cause.- Plato, Timaeus
  6. 6. Aristotle: systematic understanding ofnature in terms of “final causes.”Earth falls down, fire moves upward.Teilhard de Chardin: the Omega Point.Complexity grows with time,along with universal consciousness.Teleology: purpose without a plannerHerbert Spencer: evolution as amechanism of progress, both inbiology and in sociology.
  7. 7. Ancient anti-teleological approaches (atomism)Democritus, however, neglecting the final cause,reduces to necessity all the operations of nature.Now they are necessary, it is true, but yet theyare for a final cause and for the sake of what isbest in each case.- Aristotle, Generation of Animals[Atoms] shuffled and jumbled in manyways, and in the course of endless time theyare buffeted, driven along, chancing uponall motions and combinations.At last they fall into such an arrangementas would create this universe…- Lucretius, De Rerum Natura
  8. 8. Modern physics:Laws are differential equations in time.Isaac Newton:Erwin Schrödinger:
  9. 9. We may regard the present state of the universe as the effectof its past and the cause of its future.An intellect which at a certain moment would know all forcesand all positions of all items of which nature is composed…for such an intellect nothing would be uncertain and the futurejust like the past would be present before its eyes.- An Essay on Probabilities, 1814Pierre-Simon Laplace:the present state of the universedetermines its evolution.Laplace’s Demon.
  10. 10. Varieties of predictive theoriesHistorical Teleological Laplaciantimefuturepresentpastgoalthe past and presenttogether determinethe futurefrom the presentwe move towardsome future goalconservation of information:every moment determinesevery other moment
  11. 11. electronprotongravityelectro-magnetism(photons)nuclearforceFundamental physics c. 1935:three particles, three forcesneutron
  12. 12. electronquarksgravityelectro-magnetism(photons)strongnuclearforce(gluons)downupupupdowndownweaknuclearforce(W, Z bosons)neutrinoFundamental physics today:four particles (× 3 generations),four forces, antiparticles, Higgs fieldbackgroundHiggs field
  13. 13. Standard Model of particle physics + General Relativitygives us a working theory of “fundamental” physics.1. Internally complete and coherent.2. Uncontradicted by any experiment ever conductedhere on Earth.3. Settled, as far as the physics underlying everydayexperience is concerned.
  14. 14. gravityother forces matter Higgsquantum mechanics spacetimeThe physics underlying everyday realityNo sign of teleology, purpose, design.
  15. 15. Amplitude = number of particles or strength of force.Wavelength = mass of particle or range of force.wavelengthamplitudeQuantum Field Theory:the basis of modern physicsQuantum field are the fundamental ingredients ofreality; particles are what we see when we observethe fields.
  16. 16. QFT lets us quantify thescope of our understanding.stronglyinteractinglight/long range/low energyheavy/short range/high energyweaklyinteractingaccessibleinaccessibleknownknownsknownunknownsKen WilsonNobel 1982
  17. 17. Quantum field theory puts very tightconstraints on new phenomena.timenew particlenewinteractionIf a new particle caninteract with ordinaryparticles:Then that particlecan be created inhigh-energy collisions.
  18. 18. Could new particles hide from our view?Sure, if either:1. very weakly interacting,2. too heavy to create, or3. too short-lived to detect.In any of those cases, the new particle wouldbe irrelevant to our everyday lives.
  19. 19. Could there be new forces of nature?Sure, but they must interact with protons, neutrons,and electrons.Experiments are ongoing (torsion balances) tosearch for new, weak, long-range forces.Two ways to hide:1. weak interactions, or2. very short ranges.
  20. 20. Experimental constraints on new forces.Strength(relativetogravity)Range [Schlamminger et al. 2008]AllowedRuled Out
  21. 21. Laws of physics underlyingthe experiences of our everyday livesare completely known.
  22. 22. We don’t understand all of fundamental physicsby any means!Perfectly obvious but necessary caveats“Fundamental” doesn’t mean “interesting.”It certainly doesn’t mean “useful.” Lower-levelknowledge is often useless at higher level.“Deriving” higher-level theories is often not aworthwhile endeavor.
  23. 23. Implications of this equation:Nevertheless, there can be definite higher-levelconsequences of lower-level theories.There is no life after death; no mechanism bywhich the soul can survive the body.Astrology is wrong.Electric charge is conserved.
  24. 24. Multiple different levels of descriptionseem to usefully talk about reality(theories/models/vocabularies/ontologies/stories)Cartoon:particlephysicschemistry biologysocialsciencesWhat counts as “fundamental”? What is “emergent”?Which theories entail, supervene on, or explain whichother theories?
  25. 25. A coarse-grained (“emergent”) theory may capturepart of an underlying theory in a more efficient form.kinetic theory/statistical mechanicsO(1030) equationsfluid mechanics/thermodynamicsO(1) equations
  26. 26. Higher level theories can have a fundamentallydifferent character than lower-level theories theyare purportedly entailed by.Emergent featuresE.g. the arrow of time.Thermodynamics has an arrowof time, while mechanics does not.Ultimately because the universecomes with a low-entropy pastboundary condition.time
  27. 27. timeIndeed, there is no obstacle to higher-level theoriesbeing teleological, even if the lower-level theory is not.Teleology can be thought ofas a future boundary condition.No more bizarre than thepast boundary condition wethink actually exists.Should we speak teleologically?Yes, if it’s the most efficient description for a level.
  28. 28. Higher-level vocabulary might be completely differentin character than underlying (“fundamental”) description.“The cat is trying to catch the mouse” is enormouslymore informative than a list of all the elementary particlesin the cat/mouse system, plus the laws of particle physics.
  29. 29. Natural selection and emergent teleologyDarwin explained the appearanceof design via natural, impersonalprocesses. Evolution has no purpose.But organisms (or traits) can havepurposes, if invoking them provides thebest explanation. No designer implied.No contradiction between saying“evolution has no purpose” and“organisms have purposes”;just different vocabularies fordifferent levels of description.
  30. 30. The job of science is to describe the world.There are other things we might want to do.Judgment, aesthetics. Ethics, morality.The meaning of life.An entirely different kind of story. Must becompatible with science, but not reducible to it.Resist the temptation to think science is all there is.Science and values:description vs. prescription
  31. 31. Where do judgments come from?(Good without God.)Lots of places. Human beings are not blank slates.They come equipped with desires, aspirations,preferences, emotional reactions. From biologyas well as from culture.Moral philosophy isn’t about proving universaltruths. It’s about taking our existing moral feelingsand developing them into something logical,systematic, and compatible with those of otherpeople.
  32. 32. Developing theories of value is a matter of telling thestories that best encapsulate our existing desires etc.Subjective, but not arbitrary!“The universe is made of stories,not of atoms.” - Muriel RukeyserFinding meaning in life is an essentially creative act.We bring purpose into the world;it is not out there to be found.
  33. 33. Consider chess.The rules of chess don’t inhere inthe fundamental laws of physics.We invented them; they could beotherwise. They are subjective.But they are not arbitrary. They are carefully adjustedto serve a purpose: the most interesting game.Likewise for (e.g.) morality. Invented, but not at allarbitrary. Our notions of morality are carefully adjustedto serve a purpose: our notions of justice and fairness.[Alan Light/Wikipedia]
  34. 34. Two fundamentallydifferent views ongay marriage.2) How to live is a decision we human beings haveto make. No configuration is naturally correct.We decide how to best guarantee happinessand protect individual dignity.1) There is a “natural” and correct way for humansto live. There is a natural and correct formof marriage. One man, one woman.
  35. 35. Rick Warren was wrong:it actually is all about you.Neither the universe, nor anything outside it,provides you with a purpose in life.But you can choose one for yourself.(As long as your reasoning is compatible with howthe universe works.)

×