The error of free will, Rée claims, lies behind the development of the feeling of justice: "The feeling of justice thus arises out of two errors, namely, because the punishments inflicted by authorities and educators appear as acts of retribution, and because people believe in the freedom of the will." (Rée [1877] 2003) Rée rejected metaphysical explanations of good and evil; he thought that the best explanations were those of offered by Darwin and Lamarck, who had traced moral phenomena back to their natural causes. Rée argued that our moral sentiments were the result of changes that had occurred over the course of many generations. Like Lamarck and Darwin, Rée argued that acquired habits could be passed to later generations as innate characteristics. As an acquired habit, altruistic behavior eventually became an innate characteristic. Altruistic behavior was so beneficial, Rée claimed, that it came to be praised unconditionally, as something good in itself, apart from its outcomes.