Download Philosophy of Mind Spring 06 Francesco Orilia

Philosophy of Mind
Spring 06
Francesco Orilia
Lecture 5
January 31, 2006
Excursus on identity
statements: basic facts
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the morning star is the evening star
the morning star is a planet
John believes that the morning star is a planet
-------------------------------------------the evening star is a planet!
John believes that the evening star is a
planet???
 Substitutivity of identicals is OK in extensional
contexts but fails in intensional contexts
 MS =df last visible celestial body in the morning
 ES =df first visible celestial body in the evening
Account of identity statements
 “the MS is the ES” means that the individual concept THE
MS and the individual concept THE ES, albeit different
concepts, correspond to one entity x, in that x is the
ONLY entity which has the property MS and x is also the
ONLY entity which has the property ES
 By saying “the MS is F” or “the ES is F”, we attribute the
property F to this one entity x
 But by saying “John believes that the MS is F” we are not
attributing a property to x, but to the concept THE MS.
We are saying that it is such that: according to John, it
(the concept) corresponds to one entity that has property
F. But the concept THE MS is DIFFERENT from the
concept THE ES, and thus “John believes that the MS is
F” does not imply “John believes that the ES is F”
 Frege and Russell provide different formal accounts
Identity statements about
properties
 Similarly, “being water is being H20” means that the
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concepts WATER and H20, albeit different, correspond to
the one entity h (a wordly property)
The “correspondence” in question here is probably not
quite like the one involved in the morning star case
(explainable with Russell’s theory of descriptions), but still
it is intuitively clear
If we assume that “being water” and “being H20” stand
directly for the wordly property f (rigid designation), then
“is” should mean: =
If we assume that “being water” and “being H20” stand for
concepts, then we must assume that “is” does not stand
for =, but for the correspondence relation (call it “”)
The former option makes it unclear why “water is H20” is
informative and “water is water” is not. I prefer the latter
The heat case
 The thermodynamic concept of heat is that of a property
coming in different degrees which are measurable with
the mercury thermometer
 The statistical mechanics concept of mean molecular
energy is that of a property coming in different degrees
which are measurable (roughly) by observing the speed
of gas molecules
 We observe systematic correlations. Consider the BoyleCharles law of thermodynamics: kT = pV. There is an
“image” in SM: 2E/3 = pV
 In terms of properties: gas g has a pressure  volume pV
 gas g has a temperature kT, and gas g has a pressure
 volume pV  gas g has a m.m.e. 2E/3
Bridge laws postulate an
identity
 The observed correlation suggests a Bridge
law: 2E/3 = kT
 In terms of concepts: having m.m.e. 2E/3 
having temperature kT
 In terms of wordly properties: having m.m.e.
2E/3 = having temperature kT
 Given the bridge law, we can logically derive
the Boyle-Charles law of thermodynamics, kT =
pV, from the SM fact that 2E/3 = pV
Use of bridge laws
 (1) Observed correlation: gas g has a pressure  volume
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pV  gas g has a m.m.e. 2E/3
(2) Bridge Law: having m.m.e. 2E/3  having temperature
kT
--------------------------------------(3) Charles-Boyle law: gas g has a pressure  volume pV
 gas g has a temperature kT (since (1) is extensional,
we can substitute in it, given (2), “has a m.m.e. 2E/3” with
“has a temperature kT”)
Similarly, we can logically derive other
explanations/predictions about thermodinamical facts
from explanations/predictions about SM facts
Why identity and reduction?
 The identification of heat with m.m.e. seems to be the
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most plausible and economic answer to the question
Why is there this observed correlation of heat and
m.m.e?
These answers are far more implausible:
It is an accident, a coincidence
There is common cause for both heat and m.m.e.
We say that heat (thermodynamics) has been reduced to
m.m.e. (MS), and not vice versa, because MS has more
predictive/explanatory power than thermodynamics (see
E. Nagel, The Structure of Science, 1961, ch. 11, Laird
Addis, The Logic of Society, 1975, Chs. 4-5, G.
Bergmann, Philosophy of science, 1957)
Prediction
 General law: every amount of water boils
at 100 degrees C
 Specific observed fact: this amount of
water will have temperature 100 degree
C in 1 second
 LOGICALLY DEDUCED prediction: this
amount of water will boil in 1 second
Explanation
 Observed fact to be explained: this amount of
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water is boiling.
It can be LOGICALLY DEDUCED from:
General law: every amount of water boils at 100
degree C
Background condition: this amount of water has
a temperature of 100 degree C
See C. Hempel, Aspects of Scientific
Explanation