GalileoDescartesLeibnizThe argument from sufficient reasonThe argument from indiscernabilityThe methodological argumentGalileoDescartesLeibnizSpace: the classical debateChristian Wüthrichhttp://philosophy.ucsd.edu/faculty/wuthrich/146 Philosophy of PhysicsClass 10, 30 October 2007Christian Wüthrich Class 10GalileoDescartesLeibnizSpace: the classical debateChristian Wüthrich Class 10GalileoDescartesLeibnizNewton: space is1infinite, infinitely divisible2perfectly uniform3Euclidean in geometrical structure4entity in its own right, a “substance”Leibniz: space is1something merely relative, as time is2order of coexistences, as time is order of successions3not absolute, not a substanceNewton believed existence of absolute space could beestablished on empirical grounds alone, something naturallydenied by LeibnizChristian Wüthrich Class 10GalileoDescartesLeibnizGalileo Galilei (1564-1642)Italian physicist,mathematician, astronomer,philosophersystematic studies in uniformaccelerated motion (inclinedplane, free fall)development of new physicsreplacing predominantAristotelian approachdiscovery of moons of Jupiterearly advocate ofCopernicanismChristian Wüthrich Class 10GalileoDescartesLeibnizDe motu (ca. 1590): medieval impetus theoryDialogo sopra i due Massimi Sistemi del Mondo Tolemaicoe Copernicano (1630/32): treatment of the ship mastexperiment, concept of circular inertiaDiscorsi e Dimostrazioni Matematiche intorno a due nuovescienze (1638): (theory of elasticity and kinematics) cleardevelopment toward a rectilinear concept of inertia, which,however, does not yet appear in Newtonian clarity andprominenceChristian Wüthrich Class 10GalileoDescartesLeibnizThe case against Peripatetic philosophyMajor problem for heliocentrists: common sense and prevalentphysical thy claim that Earth cannot be moving given theappearances⇒ heliocentrists need new physical thy of motionChristian Wüthrich Class 10GalileoDescartesLeibnizThe ship mast experimentGiordano Bruno, The Ash Wednesday Supper, 1584(Third Dialogue, Fifth Proposition)discusses Tower Experimentagainst heliocentrismrebuts it by Ship MastExperimentoriginally invented by C12scholasticsinstrumental in developmentof modern concept of inertiawas a thought experimentuntil Pierre Gassendi finallyperformed it in mid-C16Christian Wüthrich Class 10GalileoDescartesLeibnizNewton’s three laws of motion(cited from the Motte translation)Law (I—law of inertia)“Every body perseveres in its state of rest, or of uniform motion in aright line, unless it is compelled to change that state by forcesimpressed thereon.”Law (II)“The alteration of motion is ever proportional to the motive forceimpressed: and is made in the direction of the right line in which thatforce is impressed.”Law (III)“To every action there is always opposed an equal reaction: or themutual actions of two bodies upon each other are always equal, anddirected to contrary parts.”Christian Wüthrich Class 10GalileoDescartesLeibnizRené Descartes (1596-1650)French philosopher,mathematician, scientistLe Monde (The World), 1633,suppressedPrincipia Philosophiae (ThePrinciples of Philosophy),1644Anti-Aristotelianismexplanation entirely inmechanical termsChristian Wüthrich Class 10GalileoDescartesLeibnizexterminated some of the relicts of Aristotelianism inGalileo such as circular motion being natural and,correspondingly, circular inertia⇒ several key ingredients of Newtonian physics in place:1principle of inertia2conservation principles3methodological tenet of mechanical philosophy (no occultforces)confused conception of spaceChristian Wüthrich Class 10GalileoDescartesLeibnizThe argument from sufficient reasonThe argument from indiscernabilityThe methodological argumentGottfried Wilhelm Leibniz (1646-1716)German polymath(mathematician, naturalphilosopher, legal scholar,theologian, political advisor,historian)rationalism: reason as ultimatearbiter of justification ofknowledgeoptimism: God created the bestof all possible worldscalculus, binary numeral system,etcLeibniz-Clarke correspondence(1715-16)Christian Wüthrich Class 10GalileoDescartesLeibnizThe argument from sufficient reasonThe argument from indiscernabilityThe methodological argumentDifferent kinds of shifts1static shift: shift location of all material bodies uniformly inone direction which changing the relative distances andmotions among them2kinematic shift: change the state of motion of all mater ialbodies such that all relative distances and motions amongthem remain the same3dynamic shift: subject all material bodies in universe toforce such that they are all accelerated by the sameamount in the same direction without changing the relativedistances or motions among themChristian Wüthrich Class 10GalileoDescartesLeibnizThe argument from sufficient reasonThe argument from indiscernabilityThe methodological argumentGalilean framesGalilean frames: reference frame that are either at rest, ormoving uniformly with respect to one anotheruniform motion: rectilinear motion at constant velocitywith Newtonian absolute space: any Galilean frame is insome state of absolute motion which is uniformconsider e.g. Newton’s law of universal gravitation:FG= GNm1m2r2⇒ makes no reference to absolute position, velocityturns out all Newtonian physics is like that⇒ undetectability of both static and kinematic shiftsChristian Wüthrich Class 10GalileoDescartesLeibnizThe argument from sufficient reasonThe argument from indiscernabilityThe methodological argumentThe argument from sufficient reasonPrinciple (of Sufficient Reason (PSR))“Nothing happens without a sufficient reason why it should beso, rather than otherwise.” (cited according to Dainton, 165)assume that even God is subject to PSR, i.e. assume thatGod does nothing for which he lacks good reason⇒ God cannot create substantival space on pain of beingfaced with a choice for which there is no sufficient reasonfor favouring one alternative over the otherstheologically loaded argumentChristian Wüthrich Class 10GalileoDescartesLeibnizThe argument from sufficient reasonThe argument from indiscernabilityThe methodological argumentThe argument from indiscernabilityPrinciple (of the Identity of Indiscernibles (PII))Any two entities which have the same genuine properties areidentical.1Substantivalists claim that the two possible worlds eitherrelated to one another by a static or kinematic shift asdescribed above are distinct. (Premise to be reduced toabsurdity)2Two possible