Rietdijk-Putnam argumentCan the dynamist recover?CompatibilismIncompatibilismRietdijk-Putnam argumentCan the dynamist recover?Relativity and RealityChristian Wüthrichhttp://philosophy.ucsd.edu/faculty/wuthrich/146 Philosophy of PhysicsClass 17, 27 November 2007Christian Wüthrich Class 17Rietdijk-Putnam argumentCan the dynamist recover?The threat from SRDefinition (Classical dynamic models (CDMs))A model of time is a classical dynamic model just in case itposits an absolute and universal present, and thus an absoluteand universal front of becoming or annihilation.Examples of CDMs: presentism, growing block universespatially extended present: set of all spt points (“events”)which are simultaneous with the here-nowthe problem is that CDMs require a metaphysically robust,objectively valid concept of “a spatially extended present”which is under serious pressure from SR given the latter’srelativity of simultaneityChristian Wüthrich Class 17Rietdijk-Putnam argumentCan the dynamist recover?The initial pressure from SRCDMs: division bw what is present and non-present bearsontological significanceSR: what is present (i.e. simultaneous with here-now) andnon-present (not simultaneous with here-now) depends onarbitrary choice of reference frame⇒ seems as if SR implied that an advocate of a CDM iscommitted to a relativization of reality: what’s real dependson observerChristian Wüthrich Class 17Rietdijk-Putnam argumentCan the dynamist recover?The Rietdijk-Putnam argumentcf. Howard Stein, “On Relativity Theory and Openness of the Future”, Philosophy of Science 58 (1991): 147-167.Premises:1“The fundamental entity, relative to which the distinction ofthe ‘already definite’ from the ‘still unsettled’ is to be made,is the here and now; that is, the space-time point...” (Stein,148)2There is a relation R “being real with respect to”. Thisrelation Rxy is anequivalence relation, i.e. it is1reflexive: Rxx, a thing is real wrt itself2symmetrical: if Rxy, then Ryx3transitive: if Rxy and Ryz, then RxzChristian Wüthrich Class 17Rietdijk-Putnam argumentCan the dynamist recover?Roger Penrose’s versioncf. Steven Savitt, “Being and becoming in modern physics”, in E. Zalta (ed), Stanford Encycl. of Philosophy, 2006.Andromeda galaxy ≈ two million light yrs(or 2 × 1019km from Earth, at rest wrt toEarthon Earth Alice and Bob walk past oneanother on the Earth-Andromeda line,Alice towards Andromeda, Bob awayfrom it, each at 4km/hcall the spt point where they meet O⇒ their hyperplanes of simultaneity intersectworldline of Andromeda about 5.75 daysapart (events A and B)imagine that during this 5.75d period amomentous event happens onAndromeda, such as Andromedeanslaunch space fleet aimed at invadingEarth⇒ for Alice this event has already occurred,but not for Bob!Christian Wüthrich Class 17Rietdijk-Putnam argumentCan the dynamist recover?Rietdijk-Putnam Argument Iett0x0axChristian Wüthrich Class 17Rietdijk-Putnam argumentCan the dynamist recover?Rietdijk-Putnam Argument IItx0xebt0e0Christian Wüthrich Class 17Rietdijk-Putnam argumentCan the dynamist recover?Putnam’s conclusionHilary Putnam, “Time and physical geometry”, Journal of Philosophy 64 (1967): 240-247.“I conclude that the problem of the reality and determinatenessof future events is now solved. Moreover, it is solved by physicsand not philosophy... Indeed, I do not believe that there are anylonger any philosophical problems about Time; there is only thephysical problem of determining the exact physical geometry ofthe four-dimensional continuum that we inhabit.” (247,emphasis in original)Christian Wüthrich Class 17Rietdijk-Putnam argumentCan the dynamist recover?CompatibilismIncompatibilismCan the dynamist recover?In principle two types of strategies:1Non-compatibilism: reject SR, as least in its standard form2Compatibilism: try to reconcile CDM account with SRChristian Wüthrich Class 17Rietdijk-Putnam argumentCan the dynamist recover?CompatibilismIncompatibilismCompatibilismGeneral compatibilist strategies for saving dynamic accounts:1(Sklar) deny transitivity of the relation “being real wrt”(motivated by idea that SR shows that simultaneity relationalso fails to be transitive)2(Sklar) Spacetime solipsism: spatially distant events are asunreal as temporally distant ones3Modify presentist position: real are those events on pastlight cone (motivation via their epistemic accessibility, andthe invariant character of the light cone structure in SR)Note that CDMs are not compatible with (2) and (3)—there nolonger is an absolute and universal becoming.Christian Wüthrich Class 17Rietdijk-Putnam argumentCan the dynamist recover?CompatibilismIncompatibilismHoward Stein: the feasability of (3)Assuming the premises of the Rietdijk-Putnam argument (exceptsymmetry of R), and a time orientation in Minkowski spacetime,only one option remains for reconciling SR with an “open future”:for any given point x, the only points that are “definite as of x”are those on or inside the past light cone of x (and x itself)all other points are not definite as of x⇒ relativization of becoming to individual spt points⇒ “fragmentation” of reality, i.e. for every point in spt, a different setof points are real or definite⇒ Rietdijk-Putnam argument does not rule out possibility ofbecoming entirely, only constrains itNote: “being definite as of” is transitive, but no longersymmetricalChristian Wüthrich Class 17Rietdijk-Putnam argumentCan the dynamist recover?CompatibilismIncompatibilismLight cone becomingChristian Wüthrich Class 17Rietdijk-Putnam argumentCan the dynamist recover?CompatibilismIncompatibilismLight cone presentismStein’s light cone becoming not congenial home for presentism⇒ hollow past light cone: only events on surface of past light coneare real as of xepistemic accessibility: what’s on past light cone is what you seenowbut: symmetry and transitivity of relation “is real for” must bedeniedsymmetry can be regained by extending reality to future lightcone; but in what sense would this still be the present?⇒ not very attractive residue of presentist intuition⇒ “refusnik strategy” (Dainton, 277)Christian Wüthrich Class 17Rietdijk-Putnam argumentCan the dynamist recover?CompatibilismIncompatibilismIncompatibilismidea: since there is an absolute and universal present, SR mustbe wrong, or at least be modifiedbut: metaphysical preferences in themselves weak advocatesagainst