Chemistry Reference
In-Depth Information
that represent the substance
s chemical reactivities, which in turn are modeled by a
growing set of standardized reaction mechanisms. The theory does not only provide
explanations and predictions of chemical properties, it also allows planning and
guiding chemical synthesis of hitherto unknown compounds. Indeed, tens of mil-
lions of new compounds have been predicted and synthesized by that approach. In
contrast, quantum chemical modeling of molecular structure provides a unique
approach to the explanation and prediction of electromagnetic and many thermo-
dynamic properties, but is still rather poor regarding chemical transformations. That
is not only a theoretical division of labor according to different kinds of properties
to be dealt with by different approaches. The case of chemical structure theory
illustrates that chemistry is not only about explanations and predictions. Instead,
theoretical concepts are also developed and judged here according to their potential
for synthesis, a major activity of chemists for various, mostly nontechnological
ends (Schummer
1997
,
2004
). Moreover, theoretical concepts are expected to
provide a basis for classification, to distinguish unambiguously between myriads
of substances (Schummer
2002
). The various subdisciplines of chemistry have
further developed dozens of different kinds of molecular models and representa-
tions, from solid state chemistry to biochemistry, that each serves specific disci-
plinary needs and purposes (Hoffmann and Laszlo
1991
).
'
5.4 The Inevitability of Pluralism
There are two reasons why methodological pluralism is inevitable in chemistry: one
relates to its multiple purposes, the other is grounded in the limits of chemical
knowledge as a matter of principle.
The first reason is obvious from the aforementioned. Because chemistry pursues
different goals, we need specialized approaches to achieve each one best. The
argument requires different aims being logically independent from each other,
such that achieving one does not automatically achieve the other. Although that is
difficult to demonstrate in general, one can show at least for some instances that the
simultaneous pursuit of different goals can easily run into conflicts. For example, a
useful classification requires distinctive qualitative concepts, whereas precise pre-
dictions necessitate quantitative concepts. If synthesis is the main aim, all concepts
must be operational such that theoretical conclusions can be translated into exper-
imental operations, which is not required for classification, prediction, and expla-
nation. Explanations in turn need causal concepts that are frequently obsolete in
classification. Pursuing technological aims requires at least some utilitarian con-
cepts that are useless and sometimes distorting in other projects, and so on.
If we accept the pluralism of aims or purposes in chemistry, we must reject the
idea that there is a superior aim, say TRUTH, whose eventual achievement would
automatically meet all the other epistemic needs best. Such a superior aim is not
known in chemistry. If somebody claimed that, it could only be either the logical
combination of all known aims, and thus would be obsolete, or the favorite purpose of
