Wednesday, May 27, 2009

Against reductionism in chemistry: Hoffmann

Roald Hoffmann shared the Nobel Prize in Chemistry in 1981 and has spent his career using quantum theory to gain insight into molecular structures and reactivity. Yet, in his beautiful book The Same and Not the Same (Columbia, 1995, pp. 19-20) he argues against reductionism:
“Scientists have bought the reductionist mode of thinking as their guiding ideology. Yet this philosophy bears so little relationship to the reality within which scientists themselves operate. And it carries potential danger to the discourse of scientists with the rest of society….

There are vertical and horizontal ways of understanding. The vertical way is by reducing a phenomenon to something deeper –classical reductionism. The horizontal way is by analysing the phenomenon within its own discipline and seeing its relationships to other concepts of equal complexity.

…..there are concepts in chemistry which are not reducible to physics. Or if they are so reduced, they lose much that is interesting about them. I would ask the reader who is a chemist to think of ideas such as aromaticity, acidity and basicity, the concept of a functional group, or a substituent effect. Those constructs have a tendency to wilt at the edges as one tries to define them too closely. They cannot be mathematicisized, they cannot be defined unambigously. But they are of fantastic utility to our science.”


  1. But shouldn't we at least try, in every case, to understand vertically? I can see that horizontal understanding might be the only practical option, and that we should be concerned about destruction in reduction. But I'd think that vertical understanding is preferable whenever possible since it means thinner textbooks.

  2. Thinner textbooks, maybe, but easier end-of-chapter exercises? Compressing information past a certain point means that you pay with complication in the uncompression - working out dihydrogen dissociation from string theory may take a few pages...

    Maybe I should read Hoffman's book. The title is tantalizing, and resonates with my recent thinking. The question is one of information balance - to create a way of viewing phenomena that works in an open neighboorhood of a specific case. A good example might be an empirical law that works for a homologous series of molecules. "Homologous series" here implicitly means "open neighboorhood" in some set of chemical structures on which a topology has been imposed or inferred by the modeller. Of course the key word here is "open". If the neighborhood were closed then theoretical chemistry would be easier - but also much less interesting.

  3. Hi,

    We have just added your latest post "Against reductionism in chemistry: Hoffmann" to our Directory of Science . You can check the inclusion of the post here . We are delighted to invite you to submit all your future posts to the directory and get a huge base of visitors to your website.

    Warm Regards Team