The family migrated to New Zealand in 1868 and young Isaac was educated at Dunedin, where he was a diligent and enthusiastic student.
In Melbourne Selby worked as a lecturer and debater, supporting Unitarianism and teetotalism and denouncing Catholicism and the Jesuits.
[3] He ran for the House of Representatives seat of Northern Melbourne in the 1901 federal election against H. B. Higgins, blaming "the sinister hand of Rome" for his defeat.
[4] Selby returned to San Francisco in 1904 and became involved in an acrimonious divorce with his wife, who eventually won the case as well as custody of their children.
He joined the Royal Historical Society of Victoria in 1920 and in 1924 published The Old Pioneers' Memorial History of Melbourne.