 Suman Seth (2008) has argued that Sommerfeld’s dissatisfaction with the correspondence principle stemmed not so much from a commitment to formal rules as Darrigol suggests, but more from his general distrust of analogical thinking and what he took to be an illegitimate mixing of quantum and classical concepts. We see this, for example, in Sommerfeld’s 1924 article on Bohr’s atomic models, where he writes,