Chemistry Reference
In-Depth Information
the implications of multiple realizability for bridge laws. If one conceives of bridge
laws as a posteriori identity statements, then bridge laws must be biconditionals
linking kinds. That is, they must connect a chemical kind with exactly one micro-
physical kind.
10
Multiple realizability prevents this one-to-one connection.
11
But
even if the reductionist retreats to a one-to-many connection between a chemical
property and a heterogeneous set of physical properties, it is still unclear that the
desiderata of Nagelian reduction can be met. As mentioned, the reduction of
chemistry requires the derivation of chemical laws from physical laws. But it is
questionable that the relationship between the physical realizers of the functional
properties which figure in some chemical laws would have any nomic character.
Consider the chemical law that acids in reaction with metals generate a metal salt
and hydrogen. The number of compounds rendering this chemical law true is vast.
Take the following two examples (in aqueous solution):
H
2
SO
4
þ
Fe
!
FeSO
4
þ
H
2
2HCl
þ
Zn
!
ZnCl
2
þ
H
2
Now, to paraphrase Fodor (
1974
), one may say that while it is a law that sulfuric
acid in reaction with iron produces iron sulfate and hydrogen, and it is a law that
hydrogen chloride in reaction with zinc produces zinc dichloride and hydrogen, it is
not a
law
that either sulfuric acid or hydrogen chloride in reaction with either iron or
zinc produces either iron sulfate and hydrogen, or zinc dichloride and hydrogen.
This last statement is too gerrymandered to have any nomic character. Nonetheless,
the more general claim, asserting that acids in reactions with metals produce a metal
salt and hydrogen, is a law. Even if the two statements above expressing the
reactions can be construed as stating laws of physics (which is in itself problem-
atic), one could not use them to deduce the chemical
law
that acids in reaction with
metals generate a metal salt and hydrogen. Since the nomic character of this
statement (and of similar statements relating functional properties) cannot be
recovered from the reduction base, such statements - if laws at all - must be
regarded as
sui generis
chemical laws.
The functional, multiply realizable chemical properties may occur in higher
level chemical explanations. Q: “Why did the marble antefixes on the roof the
Philadelphia Merchants
Exchange lose their detail?” A: “Because of the acid rain.”
I take it that this is a perfectly satisfactory explanation. The answer successfully
selects one of the contrast classes (chemical) and eliminates the others (mechanical,
temperature variations, etc.). Admittedly, the explanation is not specific; it does not
mention the precise composition of the acid rain, and it leaves out the specific
chemical reactions. But this is not necessarily a defect of the explanation; in fact, it
'
10
I am assuming a strong connection between kinds and properties.
11
Of course, one may reply by saying that bridge laws need not be biconditionals. But there are
many problems with this move, and this is not the place to discuss them. I will just mention Fodor
who writes that if the relation in the bridge law “is interpreted as any relation other than identity, the
truth of reductivism will only guaranty the truth of a weak version of physicalism” (
1974
,p.99).
