The growing block universeBroad's conceptionGeneral issues with dynamic conceptionsAnother possibilist accountBack to the growing blockPresentismSolipsistic presentismMany-worlds presentismDynamic presentismCompound presentismThe growing block universePresentismDynamic timeChristian Wüthrichhttp://philosophy.ucsd.edu/faculty/wuthrich/146 Philosophy of PhysicsClass 6, 16 October 2007Christian Wüthrich Class 6The growing block universePresentismBroad’s conceptionGeneral issues with dynamic conceptionsAnother possibilist accountBack to the growing blockC D Broad (1887-1971): growing block universeScientific thought (1923)dynamic alternative to the naturalview: growing block universelike meat slicer more and more“slices” of reality are accumulatedprimitive, fundamental absolutebecomingcontemporary defender of similarview: Michael TooleyChristian Wüthrich Class 6The growing block universePresentismBroad’s conceptionGeneral issues with dynamic conceptionsAnother possibilist accountBack to the growing block“The past is thus as real as the present. [...T]he essence of apresent event is, not that it precedes future events, but thatthere is quite literally nothing to which it has the relation ofprecedence. The sum total of existence is always increasing,and it is this which gives the time-series a sense as well as anorder. A moment t is later than a moment t∗if the sum total ofexistence at t includes the sum total of existence at t∗togetherwith something more.” (1923, 88f)Christian Wüthrich Class 6The growing block universePresentismBroad’s conceptionGeneral issues with dynamic conceptionsAnother possibilist accountBack to the growing blockChristian Wüthrich Class 6The growing block universePresentismBroad’s conceptionGeneral issues with dynamic conceptionsAnother possibilist accountBack to the growing blockIncremental or continuous becoming?Two options:1slices are instantaneous, becoming continuous2slices have finite, but minimal duration, becoming isincrementalBut there’s another issue...Christian Wüthrich Class 6The growing block universePresentismBroad’s conceptionGeneral issues with dynamic conceptionsAnother possibilist accountBack to the growing blockHow fast does the universe grow?One second per second?!?But, this would only be meaningful if there would be somesort of time independent of becoming, a kind ofbackground time wrt which becoming occurs at a certainrate:One second1per second2, where second1and second2are units of different times: second2is a measure of thepre-existing background time, while we express inseconds1how much has become during a unit of thisbackground time.Important: without the existence of such a backgroundtime, the question asked above is not meaningful.Christian Wüthrich Class 6The growing block universePresentismBroad’s conceptionGeneral issues with dynamic conceptionsAnother possibilist accountBack to the growing blockNo pre-existing substantival timeGrowing block universe cannot grow by filling pre-existingtimes with events on pain of an overdetermination problemOverdetermination problem: if there exist such pre-existingtimes, they will possess incompatible attributes of beingempty (they’re not yet filled), and not being empty (oncethey’re filled)⇒ moments of time come into being together with the eventsand objects they contain, i.e. there are no future momentsChristian Wüthrich Class 6The growing block universePresentismBroad’s conceptionGeneral issues with dynamic conceptionsAnother possibilist accountBack to the growing blockRemnants of the overdetermination problemDainton claims that there still are inconsistencies:1The sum total of existence to which an event e at t1belongsconsists of S1.2The sum total of existence to which an event e at t1belongsconsists of S2.where Siis the sum total of existence at tiand t2is laterthan t1.Resolution (Tooley 1997):Proposition: accept notion of being actual as of a particulartime as ontological primitive and truth as of a time as asemantic primitive.Consequences:1same proposition can have different truth-values at differenttimes2three truth-values: true, false, and indeterminateChristian Wüthrich Class 6The growing block universePresentismBroad’s conceptionGeneral issues with dynamic conceptionsAnother possibilist accountBack to the growing blockStorrs McCall’s thinning treecaptures intuition that past is fixed, present is real andtransitory and future is as yet undetermined and openbasis idea: attrition of modal branchesChristian Wüthrich Class 6The growing block universePresentismBroad’s conceptionGeneral issues with dynamic conceptionsAnother possibilist accountBack to the growing blockHow many branches to the tree? depends: number oflogical possibilities > number of physical possibilities; ifuniverse nomologically deterministic: one branch onlyHow fast does attrition proceed?Christian Wüthrich Class 6The growing block universePresentismBroad’s conceptionGeneral issues with dynamic conceptionsAnother possibilist accountBack to the growing blockHow can a block grow?Question: what guarantees that the block grows rather thanshrinks? Consider the following inequivalent situations in auniverse with three time slices S1, S2, S3at three times t1, t2, t3:1Starting at t1with S1, the process of absolute becomingsuccessively produces S2at t2and S3at t3.2Starting as of t3with S1, S2, S3, the process of absoluteannihilation successively extinguishes S3at t3and S2at t2,leaving at t1a sum total of existence consisting of S1.Both scenarios are sequential, which sequence is temporal?Problem: with independent justification to choose one directionof time over the other, both scenarios accurately describe thisuniverse!Christian Wüthrich Class 6The growing block universePresentismBroad’s conceptionGeneral issues with dynamic conceptionsAnother possibilist accountBack to the growing blockBroad’s answerStipulate that times of larger blocks are later than times ofsmaller blocks!But how can such a stipulation be justified?perhaps via content-asymmetries: if direction indicated bythese asymmetries (fork, causation, entropy etc) coincideswith stipulation, we’re donecandidate: traces of the past but not the future and Broad’saccount explains this: times we call “future” are not real asof the times we call “present, whereas the times we call“past” areProblem: this is inconclusive, as is evidenced byconsideration involving symmetrical Gold universes⇒ still no