Al-Ghazali discusses different views on happiness and argues that true happiness is found in the afterlife, not in worldly pleasures. He outlines four types of souls - the destroyed, punished, saved, and successful - and their respective fates in Hell or Paradise. Paradise contains two grades of happiness - lower sensual pleasures and a higher nearness to God. Al-Ghazali believes knowledge and good deeds are the means to attain spiritual happiness and ensure a soul's perfection and higher afterlife rewards. Knowledge refers to understanding God and the religious practices and virtuous actions needed to purify the soul.