What role does Hume's principle (HP) play in neo-logicism?
From what I understand Frege used Hume's principle in Freges theorem to create Peano axioms from HP by using second-order logic and that Freges theorem was the basis for neo-logicism.
But I don't understand what role HP play in the neo-logicism or in what way Freges theorem was the basis for neo-logicism more than that HP led to Freges theorem that led to neo-logicism?
Help would be much appreciated!
Thanks in advance!