As a schoolboy, Gaddafi adopted the ideologies of Arab nationalism and Arab socialism, influenced in particular by Nasserism, the thought of Egyptian revolutionary and president Gamal Abdel Nasser, whom Gaddafi adopted as his hero. During the early 1970s, Gaddafi formulated his own particular approach to Arab nationalism and socialism, known as Third International Theory, which has been described as a combination of "utopian socialism, Arab nationalism, and the Third World revolutionary theory that was in vogue at the time". He laid out the principles of this Theory in the three volumes of The Green Book, in which he sought to "explain the structure of the ideal society." His Arab nationalist views led him to believe that there needed to be unity across the Arab world, combining the Arab nation under a single nation-state. He described his approach to economics as "Islamic socialism", although biographers Blundy and Lycett noted that Gaddafi's socialism had a "curiously Marxist undertone", with political scientist Sami Hajjar arguing that Gaddafi's model of socialism offered a simplification of Karl Marx and Friedrich Engels' theories. Gaddafi saw his socialist Jamahiriyah as a model for the Arab, Islamic, and non-aligned worlds to follow.