10 Sep
1999
10 Sep
'99
8:30 p.m.
ELTE TTK Tudomanytortenet es Tudomanyfilozofia Tanszek
Budapest, Pazmany P. setany 1/A
Tudomanyfilozofia Szeminarium
________________________________________________
1999. Szeptember 27. (hetfo !)
12:30
6. em. 661.
B a r r y L o e w e r
Rutgers University
Collegium Budapest
PROBABILITY AND DETERMINISM
Although probability is essential to the formulation (and evaluation) of
scientific theories and although a great deal is known about how to
employ probabilistic concepts, there is still philosophical controversy
concerning the nature of probability. Some hold that only probability
concerns only degrees of belief (either subjective or constrained by
"objective" rules) while others hold that it concerns mind-independent
features of reality. The latter view divides among those who hold that
it concerns only frequencies (actual or hypothetical) and those who hold
that it concerns a "causal propensity." The nature of probability is
especially puzzling when the underlying dynamics is completely
deterministic as in classical mechanics and Bohm's version of quantum
mechanics. Some claim that when the dynamics is deterministic then all
objective probabilities are 1 or 0. But this seems at odd with the
scientific practice. In my talk I will review some of the main ideas
concerning the nature of probability and also an idea suggested by David
Lewis. According to Lewis probability concerns an objective feature of
reality that supervenes on the totality of propositions not concerning
chance. Whether or not Lewis' account is correct for dynamical chances I
argue that it provides a good account of chance statements when the
dynamics are deterministic.
1999. oktober 4. (hetfo)
12:30
6. em. 661.
T o m a s z P l a c e k
Department of Philosophy, Jagiellonian University, Cracow
OUTCOMES IN BRANCHING SPACE-TIME (OBST)
-AN ANALYSIS OF BELL'S THEOREM-
The framework of BRANCHING SPACE-TIME (BST; cf. Belnap 1992, SYNTHESE
92, pp. 385--434) has recently been extended to allow for the
introduction of outcomes of events and the analysis of GHZ theorems.
(Kowalski & Placek, forthcoming in BRIT. J. PHIL. SCI. and INT. J.
THEOR. PHYS.)
In BST, space-time and modality are incorporated in the very structure
of the models, which consist of a pair $\langle W, \leq \rangle$, where
$W$ is a non-empty set weakly ordered by $\leq$, which is interpreted as
`causally accessible from.' Maximal upward directed subsets of $W$ are
called `histories,' and proper subsets of histories are called `events.'
Two events are called `space-like separated' if neither causally
precedes the other. `Atomic outcomes' of an event $E$ are those parts of
the event's causal future that split in $E$.
The main result of Kowalski & Placek is that the family of outcomes of
an event forms a Boolean algebra. The paper also proves that in GHZ
setups, there is always a common cause (CC) in the sense of Reichenbach
if directions are held fixed, but that there is no single COMMOM common
cause (cf. Hofer-Szabo et al., forthcoming in BRIT. J. PHIL. SCI.)
accounting for the outcomes of incompatible settings.
For an analysis of Bell's theorem, I assign probabilities to outcomes by
imposing a classical probability measure on the Boolean algebra of the
outcomes of each given event. In the derivation of Bell's theorem, I use
probability measures of the form $p_{L\alpha \cup R\beta}(Lx \cap Ry)$,
$x,y \in \{+,-\}$, where the subscript indicates that the result is an
outcome of the event of measuring the spin projections along directions
$\alpha$ on the left and $\beta$ on the right. Probabilities for single
results on the left or on the right are calculated from these measures,
allowing us to express correlations as $p_{L\alpha \cup R\beta}(Lx \cap
Ry) \neq p_{L\alpha \cup R\beta}(Lx) \times p_{L\alpha \cup
R\beta}(Ry)$.
Since correlations between space-like separated results appear
disturbing, it is natural to look for an explanation in terms of a CC
located in the results' common past. The CC's outcomes divide histories
in such a way that actual runs of a correlation experiment are seen as
belonging to two or more varieties differentiated by hidden factors. You
may think of these hidden factors as restoring the deterministic order.
You may also be more modest and require only that the hidden factors
restore the causal order, i.e., that in each sub-population, the
correlations disappear.
Formally, for space-like separated events $E$ and $F$ with correlated
outcomes $e$ and $f$, respectively, a CC is an event C preceding both
$e$ and $f$, such that for every atomic outcome $\omega_{i}$ of $C$,
$$ p_{E\cup F\cup C}(e \cap f|\omega_{i}) = p_{E\cup F\cup C}(e
|\omega_{i}) \times p_{E \cup F\cup C}(f|\omega_{i})$$,
where $p_{E \cup F \cup C}$ is defined on the enlarged probability
space. Now, for any correlated pair $e,f$, we CAN construct
mathematically an enlarged probability space containing such a CC.
Moreover, for any finite number of correlations we CAN construct a
single large probability space containing a set of distinct CCs, each CC
taking care of one correlation. However, in the Bell/Clauser-Horne
argument, one wants something more: one postulates a single common CC
accounting for all the correlated outcomes of $L\alpha\cup R\beta$,
$L\alpha\cup R\beta--\prime$, $L\alpha--\prime\cup R\beta$, and
$L\alpha--\prime\cup R\beta--\prime$. Given the standard assumptions of
locality and `no conspiracy,' which in our framework take the form
\begin{equation*}
\begin{split}
& \forall \alpha, \beta, \varphi, x p_{L\alpha \cup R\beta\cup C}(Lx)
= p_{L\alpha \cup R\varphi\cup C}(Lx)\ & \forall \alpha, \beta, \gamma,
y p_{L\alpha \cup R\beta\cup C}(Ry) = p_{L\gamma \cup R\beta\cup
C}(Ry)
\end{split}
\tag{LOCALITY}
\end{equation*}
\begin{equation*}
\forall \alpha, \beta, \gamma, \varphi, i p_{L\alpha \cup R\beta\cup
C}(\omega_i) = p_{L\gamma \cup R\varphi\cup C}(\omega_i),
\tag{NO CONSPIRACY}
\end{equation*}
we derive the Bell/CH inequalities, which are empirically violated.
Thus, there cannot be a common common cause accounting for the Bell/CH
correlations.
1999. oktober 11. (hetfo)
12:30
6. em. 661.
E. S z a b o L a s z l o
ELTE, MTA Elmeleti Fizikai Kutato Csoport
ELTE, Tudomanytortenet es Tudomanyfilozofia Tanszek
EINSTEIN MEGOLDOTTA AZ EPR-BELL PARADOXONT?
Úgy tunik igen, sot meg egy sereg mas problemajat a kvantumelmeletnek.
"Prizma-modell" neven Arthur Fine 1982-ben egy olyan megoldast javasolt
az EPR-Bell problemara, es altalaban a kvantummechanika lokalis-realista
interpretaciojara, amelyrol, mint kesobb o maga kideritette, mar
Einstein is emlitest tett egy 1936-os cikkeben, illetve nehany Rosenhez
es Schrodingerhez irt leveleben. E megoldas nem kapott kulonosebb
visszhangot, sot maga Fine sem vette igazan komolyan, hiszen kesobbi
cikkeiben úgy ir a Bell-tetelrol, mintha az Einstein-Fine-interpretacio
nem is letezne. Ennek oka, hogy tevesen, Fine ezt a megoldast a
valosagban vegrehajtott kiserletekben hasznalt detektorok nem 100%-os
hatasfokaval hozta kapcsolatba.
Az eloadasban az Einstein-Fine-interpretaciot egy új megvilagitasban
mutatom be. Megmutatom, hogy semmi koze nincs a detektorok hatasfokanak
sokat diszkutalt problemajahoz. A valosagban elvegzett EPR-Bell
kiserletek elemzesevel megmutatom, hogy e kiserletek logikai
szerkezetuknel fogva teljesen kompatibilisek az
Einstein-Fine-interpretacioval, amely viszont tokeletesen feloldja az
EPR-Bell paradoxont.
1999. oktober 18. (hetfo)
12:30
6. em. 661.
K a t a l i n B a l o g
Yale University
CONCEIVABILITY, POSSIBILITY AND THE MIND-BODY PROBLEM
I want to take on the question of what a class of arguments, usually
called the Conceivability Arguments, have to say about the mind-body
problem. These arguments have two different versions. In one version,
considerations of conceivability are taken to support the claim that
phenomenal consciousness is not identical, realized by, or supervenient
on, physical properties (for example, Kripke 1972, 140-162, Nagel 1974,
Robinson 1993, White 1986, Jackson 1998, and Chalmers 1996). According
to the other version, there is an explanatory gap between phenomenal and
physical levels of description, that does not exist with respect to
other higher level descriptions, and that may have metaphysical
ramifications. (This argument is formulated by Joseph Levine 1998,
although he is himself hesitant to accept the conclusion.) My claim is
that these arguments do not succeed in establishing their conclusions.
That is because, and I take this to be the primary lesson of the
Conceivability Arguments, what they reveal does not have to do with
phenomenal consciousness itself, it rather has to do with the nature of
phenomenal concepts.
In the paper, I will focus on the most elaborate and sophisticated
version of the Conceivability Argument for dualism. I first provide a
general exposition of the structure of Conceivability Arguments, then I
proceed to describe in greater detail Frank Jackson's and David
Chalmers' new Conceivability Argument. Finally I construct a reductio
that at the same time reveals where the arguments went wrong.
1999. oktober 25. (hetfo)
12:30
6. em. 661.
K o v a c s G y u l a
SZOTE, Elettani Intezet
OUR BRAIN AND OUR MIND
The neuronal bases of consciousness
(Az eloadas magyarul lesz!)
1. Introduction
1.1. Definition of awareness & consciousness for the non-philosopher
1.2. "Components" of consciousness
1.3. Levels of human consciousness, coma, sleep, awake states
1.4. "Prerequisites" of consciousness
2. Recent results on the brain and mind problem
2.1. Visual consciousness
2.2. Blindsight
2.3. Perception vs. action
2.4. Bistable percepts
2.4.1. Ambiguous figures
2.4.2. Binocular rivalry
2.5. Electrical brain stimulation and conscious behavior
2.6. Subliminal and supraliminal stimulus processing
2.7. Time scale of consciousness
Humans & Monkeys:
2.8. NCC - Neural Correlate of Consciousness
Theories & models
--
Laszlo E. Szabo
Department of Theoretical Physics
Department of History and Philosophy of Science
Eotvos University, Budapest
H-1518 Budapest, Pf. 32.
Phone: (36-1)2090-555/6671
Fax: (36-1)372-2509
Home: (36-1)200-7318
http://hps.elte.hu/~leszabo