Hacham Joseph Ergas was born to Sarah and Hacham Emanuel in 1685, in Livorno, Italy. He learned Torah from his father, who was one of the city's sages, and studied in the yeshiva headed by the Rabbi of Livorno, Hacham Samuel De Pas. In 1704 he married Sarah, daughter of Abraham Miranda, and the couple had three sons and three daughters.
Hacham Joseph Ergas moved to the city of Raggio, where he studied Kabbala with kabbalist Hacham Binyamin Hacohen, Hacham Moshe ZAkut's student. He later moved to Pisa, where he founded the Neve Shalom yeshiva and several charitable institutions. Upon his return to Livorno, he was acclaimed by the community and began to officiate as its rabbi. He raised many students, including Hacham Malachi Hacohen, author of Yad Malachi, and his two sons - Hacham Emmanuel, who succeeded him as the city's rabbi, and Hacham Abraham, who published his numerous books.
His Kabbalistic thought proposed an explanation of the HAAR"I's theory of tsimtsum as a parable היוצא מידי פשוטו and was the scholarly opponent of his cousin, who also lived in Livorno, kabbalist Hacham Emmanuel Hai Ricci, author of Mishnat Hassidim.
In 1710, Hacham Nehemiah Hiya Hayoun, suspected of Shabbetaism, arrived in Livorno. Hacham Joseph Ergas opposed him until he was expelled from the city. Hacham Nehemiah Hiya Hayoun moved to Amsterdam, where he published a book of diatribe against him; Hacham Joseph Ergas wrote two books in rejoinder, Tochakhat Migolah and HaTzad Nakhash, published in 1715.
Hacham Joseph Ergas passed away in Livorno on 3 Sivan, 5490 (1730) at the age of 45. Among his writings one counts Shomer Emunim – an introduction to Kabbala, Divrei Yoseph – Responsa, Minkhat Yosef – on Kabbala, and Mevo Petakhim – on the HAAR"I's thought.