After returning to his native land he occupied himself with natural philosophy. He traveled throughout Greece to acquire a better knowledge of its cultures. He mentions many Greek philosophers in his writings, and his wealth enabled him to purchase their writings. Leucippus, the founder of atomism, was the greatest influence upon him. He also praises Anaxagoras. Diogenes Laertius says that he was friends with Hippocrates, and he quotes Demetrius saying: "It would seem that he also went to Athens and was not anxious to be recognized, because he despised fame, and that while he knew of Socrates, he was not known to Socrates, his words being, 'I came to Athens and no one knew me.'" Aristotle placed him among the pre-Socratic natural philosophers.