According to Aleister Crowley, the last Aeons within the system of Thelema were neither (1) the Aeon of Isis, (2) nor the Aeon of Osiris, but (3) the current Aeon of Horus which began in 1904 with the writing of The Book of the Law
The third aeon is the Aeon of Horus, controlled by the child god, symbolised by Horus. The first of these was the Aeon of Isis, which Thelemites believed occurred during prehistory and which saw mankind worshipping a Great Goddess, symbolised by the ancient Egyptian deity Isis. In Thelemite beliefs, this was followed by the Aeon of Osiris, a period that took place in the classical and mediaeval centuries, when humanity worshipped a singular male god, symbolised by the Egyptian god Osiris, and was therefore dominated by patriarchal values. He married Rose Edith Kelly and in 1904 they honeymooned in Cairo, Egypt, where Crowley claimed to have been contacted by a supernatural entity named Aiwass, who provided him with The Book of the Law, a sacred text that served as the basis for Thelema. 
