He attended the lectures of Karl Leonhard Reinhold and Gottlieb Hufeland, and soon published some literary essays of more than ordinary merit.

It was this step which led him to success and fame, by forcing him to turn from his favourite studies of philosophy and history to that of law, which was repugnant to him, but which offered a prospect of more rapid advancement.

Soon afterwards, in lectures on criminal jurisprudence he set forth his famous theory, that in administering justice judges should be strictly limited in their decisions by the penal code.

[1] Von Feuerbach was the originator of the famous maxim nullum crimen, nulla poena sine praevia lege poenali: "There is no crime and hence there shall not be punishment if at the time no penal law existed".

Out of his practical experience in the Ministry of Justice, with evaluating death penalties by Bavarian courts for royal pardon, he published the most notable cases 1808/11 in Merkwürdige Criminalfälle and 1828/29 a much enlarged collection Aktenmäßige Darstellung merkwürdiger Verbrechen (Notable crimes presented according to the court records).

It was at once made the basis for new codes in Württemberg and Saxe-Weimar; it was adopted in its entirety in the Grand Duchy of Oldenburg; and it was translated into Swedish by order of the king.

In 1821 he was deputed by the government to visit France, Belgium, and the Rhine provinces for the purpose of investigating their juridical institutions.

In his later years, he took a deep interest in the fate of the strange foundling Kaspar Hauser, who had excited much attention in Europe.