One of the widely studied references to the Charvaka philosophy is the Sarva-darśana-saṅgraha (etymologically all-philosophy-collection), a famous work of 14th century Advaita Vedanta philosopher Mādhava Vidyāraṇya from South India, which starts with a chapter on the Charvaka system. After invoking, in the Prologue of the book, the Hindu gods Shiva and Vishnu (by whom the earth and rest were produced), Vidyāraṇya asks, in the first chapter: