Chemistry Reference
In-Depth Information
13.7 Conclusion
One cannot ignore the idealization of causal difference-makers in chemistry.
In spite of the fact that causal processes are often misrepresented in chemistry,
some of the most important approaches to modelling the stereochemical course of
organic reactions posit non-causal dependencies and cite non-causal difference-
makers that entail their explanatory targets. If there are non-casual dependencies,
one might detach causal influence and the kairetic procedure of for determining
explanatory relevance. The result is that the symmetry control of organic reactions
is a case of non-causal explanation in chemistry which is nonetheless compatible
with the kairetic criterion of explanatory relevance, modified in that it is no longer
tied to the domain of physical causal influence.
Of course, what has been provided in this chapter is only a sketch. Much more
could be said about the connection between symmetry and explanation. But it
should be noted that this is an area that has received relatively little attention in
the philosophical literature on the foundations of physics, let alone the philosophy
of chemistry. Brading and Castellani (
2007
,
2013
) provide some useful suggestions
concerning the relationship between symmetry and explanation in physics, as well
as the ontological and epistemological status of symmetries. The latter issue is of
crucial importance to explanation too, for it will impact on what conception of
explanation - ontological or epistemological - one defends. As far as this author
can determine, however, no connection between symmetry and explanation as
difference-making has been made. The explanatory function of orbital symmetry
might be spelled out further as an application of symmetry arguments in chemistry.
An intriguing possibility (restricted to deterministic systems and admittedly subject
to interpretational difficulties and profound disagreements as to its significance) is
that there is a relationship between Woodward and Hoffmann
s essential idea of the
'
symmetry control of pericyclic reactions and “Curie
s principle”. This principle
'
arises from Pierre Curie
s interest in the connection between the physical properties
of crystals (such as their thermal, magnetic and electric properties) and symmetry;
in particular which physical phenomena are allowed to happen given the symmetry
properties of a physical medium (Brading and Castellani
2013
). Curie
'
s principle
might be simply expressed as “The symmetry of a cause is always preserved in its
effects” (Ismael
1997
, 167), or “When certain causes produce certain effects, the
symmetry elements of the causes must be preserved in the effects” (Brading and
Castellani
2007
).
9
As is well known, Curie
'
s principle is undermined by spontane-
ous symmetry breaking. But there might be enough of interest remaining in the
“principle” to explore its relationship to orbital symmetry, and that the chemical
properties of substances might be related to the symmetry properties of molecular
structure and dynamics. That might offer a means to further explore the relationship
between symmetry and causation in chemistry.
'
9
An influential interpretation of Curie
s principle is provided by Chalmers (
1970
). See also
'
Earman (
2004
).
