Modal Empiricism and Two-Dimensional Semantics
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=" Modal Empiricismand Two-DimensionalSemantics GergelyAmbrus, Miskolc, Hungary h45í2amb@he|ka.iif.hu l. The concept ofstrong necessity hold that zombies are not possible,even thoughtthey are li:, conceivab|e;víz. certain physica| (brain) events strong|y ]l"1 A strongly necessitates B, when it is not possible that A necessitateconscious events. This view is a version of a and not B, though it is conceivable that A and not B. In posteriorimaterialism, which holds that physical facts de- ..t anotherÍormu|ation: A entai|sB' but it is not priori a fuhatA terminefacts about consciousness.but thev do not deter- entails B (A does not imply B). Strong metaphysicatne- mine them a priori. cessities determine the space oÍ possib|e wor|ds. |f the T'1 space of possible worlds is sparser then the worlds which are (ideallyprimarily positively) conceivable, then whether ll. Chalmers' arguments against strong necessities a world is possible or not, is determinedby some meta- & physical fact, over and above the world's being (ideally One argument of David Chalmers against strong meta- primarily positively) conceivable.' Thus: accepting that physical necessities is the following.There are no candi- - - there are strong necessities commits one to modal empir- dates of strong necessities,except the alleged strong :l icsm;denying it, to modalrationalism. necessity of the brain-consciousnessrelation; and this 1: suggests that strong necessity is an ad froc inventionto a The concept oÍstrong necessity may be i||uminated save materialism.I shall argue, however, that it follows {. further by consideringthe relation between complete de- trom Chalmers, views on the semantics and ontology oÍ iui scriptionof a world w and a particulartrue statementS. lf, microphysica| terms, that there are some oÍherstrong ne- :l given the complete qualitativedescription of world w, S is cessities:microphysical identifications, such as,,Hydrogen true in word w considered as actual (viz. S is true. inter- is the such and such quantumstate"are strongly neces- preted according to its primaryintension), but S is not en- sary. (|fI am right,it a|so Ío||owsthat a posteriorimateria|. tai|eda priori by the comp|etequa|itative description oÍ w, ism cannot be rejected on the general assumption that then the facts described by the complete qualitativede- there are no strong metaphysicalnecessities whatsoever. scription of world w strongly determine the facts S de- However,my argumentclearly does not establishthe truth scribes. of a posteriorimaierialism, I do not have this aim here.) Whether strong metaphysicalnecessities exist, also Chalmers modal rationalistclaim that there are no have implicationsfor the consciousness-brainrelation, in strong necessities whatsoever, is elaborated in terms of the followingway. Chalmers argues that the possibilityof the followingprinciples (Chalmers 2002, 174-188): zombies is sufiicientto refute materialism.Now, zombies seems conceivable (or, at least, I will not challenge this (CP+)ldeal positive 1-Con P ) 1-Pos P assumptionhere), but are they also possible? Accordingto (CP-)ldeal negative 1-Con P ) 1-Pos P modal rationalism the conceivabilityof zombies implies their possibility,according to modal empiricism,it does not. (CP+) and (CP-) do not have the same strengthof eviden- Hence, one way of rejectingthe zombie argument is to tial support; (CP+) is almost certainly true, according to Chalmers, while (CP-) is not. This is not relevant to my r I use DavidChalmers'conceptual apparatus here. argument,however, for I shall deal primarilywith (CP+). Negatíve conceivabl/ÍyoÍ a stateménts: s is not ru|ed out by our concepts. For examp|e, is negative|yconceÍVab|e that bats have bat-experiences, radi- ca|ly diÍferentÍrom human experiences, for the concepts describing the u|tra- lll. My thesis: microphysical identificationsare sound mechanismsof bat perceotiondo not rulethis out. Positive @nceívabilv of a statement s: a positive conception can be formed strongly necessary in which S is the case, (we have the relevant notions for conceiving it). For example, zombies are positivelyconceivable: we have the notions to conceive My thesis is that there are counterexamplesto (CP+);they a beingWho is an exact physica|dup|icate oÍ a norma|human being,but has are ideally positivelyprimarily conceivable, but not primar- no Dhenomenalconsciousness. ily possible. I suggest that microphysicalidentifycation are ldeal conceivabílityis conceivabi|ityby an idea| reasoner (an idea||yrationa| being). such cases: they should count as stronglynecessary, if we Metaphysical possÍbility.What God might have created, had He so chosen adopt Chalmers' semantics and metaphysics of micro- (metaphoricallyput). For example,God could have createda mile-highunicy- physicalterms. cle, but he couldn'thave createda male vixen. Prímary intensÍon.A function rendering extensions to possib|e wor|ds consid- ered as actual. When "considering a world w as actual", we determine the My example is the claim that "Hydrogenis QM". The extension of our terms at Wor|dW as Ío||ows.We take the reÍerence-fixeroí the terms "hydrogen"and "QM" should be understoodas fol- ..hydrogen', terms in world w, and determine what they would pick out in world w, were w Iows. The reÍerence-fixerof is ..hydrogen- the actual world. Secondary intension' A Íunction rendering extensions to possib|e Worlds likeness",viz. having a certain emission spectrum, SpE; considered as counterfactual.When "consideringa world w as counterfactual", QM is a certain quantum-mechanicalstate, which is de- we take the reference-fixerof the terms in the actual world, detemine what scribed by the Schrödinger-equation,the eigen-va|uesof they picks out in the actual woÍ|d,and render these reÍerencesto world W' A statement S is primarily conceivable (1-Con\, if it is conceivable when inter- which are the energy levels correspondingto the spectrum preted according to iis primary intension' A statement s is /deaily posítively SpE. Inour world,what is hydrogen-likeis QM. pimarily conceivable, iÍ s is positive|y conceivab|e by an idea| reasoner' interpretedaccording to its primary intension' A statement itis pimaÍíly possi- Now considerthe followingargument. b/e (1.Pos)if it is possib|e(there is a possibleWoí|d in Wtrichit is hué),When jt is interpretedaccording to its pÍimaryintension. A statement s is sécondaí' (1) "Hydrogenis not QM" is ideallyprimarily positively poss/b/e (2-Pos), if it is possible, interpretedaccording to its secondary inten- sion. conceivable. There is one sing|e space oÍmetaphysica||y possib|e Wor|ds, ' )': entai|Sá pnbi. (2) lf "Hydrogenis not QM" is ideally primarilypositively (See e.g. Chalmers1996. chap. 2.) conceivable,then "Hydrogenis not QM" is primarilypos- sible. ModalEmpiricism and Two-Dimensional Semantics / GergelyAmbrus 'lHydrogen (3) lf is not QM" is primarilypossible, then The primaryintension of ,,hydrogen"is a constantfunc- "Hydrogenis notQM" is secondarilypossible. tion. Since the secondary intensionof "hydrogen"is the same as its the primary intension (it also renders QM to each "Hydrogen possible. is not QM" is secondarily possible world),therefore (3) holds: if it is primarilypos- But the conclusionmust be false. For if "Hydrogenis QM" sible that "Hydrogenis not QM", then it is also secondarily is true in our world,then it is secondarilynecessarily true possible. "Hydrogen (by re that is QM" the definitionof the secondary Now, iÍwe cannot reject (1) and (3)' then the on|y "Hydrogen lv intension of is QM"), hence it cannot be the option remainingis to reject (2). Rejecting (2) amounts to possible "Hydrogen a case that it is secondarily that is QM". rejecting(CP+)' víz.modal rationa|ism,for it is tantamount premises. e- Hence, we have to rejectone of the to the claim that while it is conceivablethat "Hydrogenis Í- not QM", it is not possible. This means, that "H is QM is The support Íorthe premises strongly necessary: hence we have a case of strong ne- cessity differentfrom the brain-consciousnessrelation As regards (í) a- Objections (1) is true' because it is noÍa priorithat,,Hydrogen is QM'. t1- We may investigatefurther whether the support for (3) is rs For all we can know a priori (in principle),do hot rule out reallyacceptable. is that "Hydrogenis not QM". After all, "Hydrogenis QM" is (i) "semantic to an empiricaltruth. And we can also conceive of a scenario expresses the so-called account of possible Against such an ts in which "Hydrogen is not QM" (namely a scenario, in consideringa world as actual". has formulatedobjections of which "Hydrogenis QM-", QM- being a microphysicalstate interpretationRobert Stalnaker (Stalnaker200'1). *. other than QM). Hence it is both negativelyand positively Ít conceivablethat "Hydrogenis not QM". As against (ii), there are several argumentative v (a) É Note that there is another conception of conceiv- strategies.one |ine is to c|aim,that the semantics oÍ is similarto the semantics of in the sense that at ability which sometimes gets mixed up with the one we ,,H" ,,wate/', its primary reference may change across worlds (As ,,wa- f. used here, namely: ,,it accords with our present know- ..Hydrogen tef' may refer to XYZ, may refer to QM* at some non- El |edge''.|Í is not QM,, were on|y conceivab|ein ,,H" I shall come back to this sense, this would not groundthat "Hydrogenis QM" is actual worlds considered as actual). this later. strongly necessary. However, "Hydrogen is not QM" is ro conceivable in the relevant sense. To see this, consider (ii) (b) of Another line against is to claim that ,,H"does the followingexample. The Goldbach-conjecture(any even not referto some categoricalproperty, but to some disposi- product primes) integeris the oÍtwo and a|so its negation tional,structural property, and this allows that ,,H"does not is conceivable,in the sense that they both accord with our denote QM, but something else in some (non-actual) present knowledge.But they both cannot accord with all worlds considered as actual. According to the now domi- what we can know a pioi in principle.For if the Goldbach- nant view,the propertiesmicrophysical theories attribute to conjectureis true, it is a prioritrue.