Chemistry Reference
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it so
variety, including but not limited to causal influence” (ibid). The “making it
so” relation (the meaning of which is up to the reader to ascertain) and the
entailment relation (or some cognate) is all that is required. On one hand, Strevens
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two-factor approach permits an ecumenical stance with respect to the metaphysics
of causation by not getting into the issue of the relation of causal influence itself.
On the other hand, modularization permits Strevens to claim that one could detach
the two factors: causal influence and the kairetic criterion of explanatory relevance
(ibid, 179). Is Strevens more committed to the difference-making criterion than the
relation of causal influence itself? Surely not. But while Strevens
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two-factor
approach entails ecumenism regarding the metaphysics of causation, his
modularism makes it all the easier to concede that not all explanation is causal
explanation. Are there any other contenders?
13.6 Symmetry and Non-causal Difference-Making
The positive suggestion to be sketched here is that there are
non
-causal dependen-
cies in quantum chemistry - dependencies not captured by the relation of causal
influence and so independent of an ontology of causes -, and this can address the
problem with explanatory idealizations construed as the misrepresentation of
causal
processes while retaining Strevens
difference-making criterion of explan-
atory relevance. At the very least, one can point to the explanatory power of an
explanation tied to a domain of non-causal influence even if models idealize the
causal story.
Let us return to the difficulties described above concerning the situation that
confronted chemists when they attempted to provide classical causal-mechanical
explanations of cycloaddition reactions and intramolecular rearrangements.
These difficulties were overcome once Fukui, and Woodward and Hoffmann
began to apply the molecular orbital theory to the study of organic reactions. Recall
that Woodward and Hoffmann recognized that the relevant class of reactions could
be described as taking place in a closed circle of bonds wherein bond breaking and
formation took place simultaneously in a single kinetic step. Woodward and
Hoffmann provided a much sought after causal mechanical explanation of a
group of reactions of crucial synthetic importance. One shouldn
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t underestimate
the importance of the importance of framework relative causal mechanical expla-
nations to chemists at that time (they still do) (Fisher
2006
). Shortly before the
introduction of the Woodward-Hoffmann approach, physical organic chemists
Doering and Roth (
1962
, p. 67) jokingly referred to “no mechanism reactions”,
thus highlighting the inability of classical mechanistic criteria to explain what
would come to be called pericyclic reactions. While the “no mechanism” designa-
tion was dropped after Woodward and Hoffmann published their ideas in a series
of papers in the mid-1960s, it is also crucial to recognise that Woodward and
Hoffmann were engaged in project that went beyond mere causal explanation.
For one thing, their selection rules for pericyclic reactions - the Woodward-
Hoffmann rules - highlighted the considerable value that chemists placed in models
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