Chemistry Reference
In-Depth Information
feature that is shared by all metal atoms and only by them is highly implausible.
Despite the fact that their microstructural descriptions are wildly heterogeneous,
metals have interesting chemical properties in common: their atoms readily lose
electrons to form positive ions; they form metallic bonds with other metal atoms
and ionic bonds with nonmetal atoms. Since the property of being a metal is not
characterized by a shared microstructure, but by what the entities instantiating the
property can do, this property is also functional.
Functional properties in chemistry are not only multiply
realized
(in the sense of
there being many systems composed of electrons and nuclei that can carry out the
specified role), but they are also multiply
realizable
- the list of systems composed
of electrons and nuclei that can carry out the specified role is open ended. Chemistry
is in the business of synthesising new substances. Although synthetic elements have
also been created, most of the synthetic substances are compounds. For any
functionally defined chemical property like acidity, chemists can come up with
new compounds which can carry out that behaviour.
If there are functional, multiply realizable properties in chemistry, then this means
that certain notions of reductionism cannot be maintained. I have already mentioned
type reductionism. Type reductionism (or, as Fodor called it, “type physicalism”) is
the idea that every property mentioned in the laws of any science is a physical
property. If type reductionismwere true, there would be a one-to-one correspondence
between chemical properties and microstructural properties. The kinds that chemistry
talks about would be shown to be identical to, or at least coextensive with, physical
kinds. For some chemical properties (like the property of being an alcohol) this is in
fact true - as stated, there is a one-to-one correspondence between alcohols and
microphysical systems containing a hydroxyl group bound to a saturated carbon
atom. But for other chemical properties (like the property of being an acid) it is
not. This suggests that properties like acidity are not physical properties in disguise;
they are
sui generis
chemical properties, i.e., chemical properties in their own right.
Acidity is made possible by physical processes at the lower level, and any instance of
acidic behaviour (i.e., any particular reaction) may be identical to (or coextensive
with) a specific physical process at the lower level. But acidity as a property
type
is
not identical to (or coextensive with) any microstructural physical property. It
emerges as a property only when one zooms out of microphysics and starts looking
not at microphysical structures, but at their behaviours.
The existence of functional properties in chemistry also impacts reductionism
about chemical laws. On Nagel
s concept of reduction (
1961
), chemistry would
reduce to physics if one could derive all the laws of chemistry from the laws of
physics together with bridge laws connecting the terms in the vocabularies of the
two sciences.
9
The philosophical literature on Nagelian reduction has long debated
'
9
In this context, by “chemical laws” I do not mean exceptionless and timeless universal truths, of
the kind that occur in fundamental physics (or maybe not even there). Rather, I mean the kind of
regularities chemists use on a daily basis, and which chemistry students find circled in chemistry
textbooks. For example, the statement that “Acids in reaction with metals generate hydrogen gas”
would count as a chemical law. If one does not accept this charitable reading of what a law should
mean, then the Nagelian reduction of chemistry to physics cannot even begin to be discussed.
