Valence bond theory identification

Nagel, Oppenheim and Putnam saw the explanatory appheation of physical laws to chemistry as the paradigm example of reduction, and it is stiU cited as such. So how accurately does classical reductionism portray the imdoubted explanatory success of physical theory within chemistry Two main examples are cited in the literature (i) the relationship between thermodynamics and statistical mechanics and (ii) the explanation of chemical valence and bonding in terms of quantum mechanics. The former reduction is widely presumed to be unproblematic because of the identification of temperature with mean molecular kinetic energy, but Needham [2009] points out that temperature can be identified with mean energy only in a molecular population at equilibrium (one displaying the Boltzmann distribution), but the Boltzmann distribution depends on temperature, so any reduction of temperature will be circular (for a survey of the issues see [van Brakel, 2000, Chapter 5]. 

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