This is the third and fourth topic of the Introduction of al-Ghazzali to his masterful work Alchemy of Happiness. In addition to knowing yourself and God, you need to have some idea about this world and the Hereafter. According to al-Ghazzali, without an understanding of the passing nature of this world and the permanence of the Hereafter, you may operate out of a different set of values than the ones with which the Creator blessed you.