Goals successive approximations toward

Successive approximations toward the goal. Rewarding small steps toward progress. 

The theory of absolute reaction rates has not and probably will not, in the foreseeable future, permit the satisfactory a priori calculation of most reaction rates, particularly in condensed phases. What it does do, instead, is to identify an attainable goal toward which speculation, semiempirical calculation, and experimental work may be directed. That is the elucidation of transition state structure. If transition state structure could be determined, by whatever means, as well as the structure of many stable molecules is now known, it would be possible to calculate reaction rates. Further, even well short of enough information to calculate rates, even very approximate and incomplete transition state structures may often suffice for the calculation of such rate-related quantities as isotope effects,Bronsted a values, and Hammett p values. When successful, such partial calculations tend to confirm the partial transition state structures on which they are based and, thus, to permit further progress on a more secure base. We cannot be certain how well pleased Henry Eyring is with this hybrid of theory and empiricism, but it doesn t seem likely that he is too disturbed. The pragmatist, pleased with what works and ready to take information from anywhere, has always seemed to be as well represented in his work as the rigorous theoretician. 

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