 This was a common belief at the time, and can also be found within the medical writings of Herodotus' times, including the "On Airs, Waters, Places" of the Hippocratic corpus.One can find a similar statement in "Germania" by Tacitus, one of Montesquieu's favorite authors.Philip M. Parker in his book "Physioeconomics" endorses Montesquieu's theory and argues that much of the economic variation between countries is explained by the physiological effect of different climates.