Mary Renault's The Persian Boy concerns Alexander III, also known as Alexander the Great, and his conquest of Persia. As a historical fiction writer, Renault is deeply concerned about presenting the truth with respect to history. Critics praise her work for the accuracy of historic details due to her meticulous research. Renault herself has said that what's most important for any historical novelist is to be honest about the facts, the truth, and the truth about human nature (eNotes, "The Persian Boy Essay--Critical Essays"). Her greatest concern was to reveal to her readers truths about human nature, which can certainly even be seen in The Persian Boy. Renault reveals truths about human nature through the social and cultural customs present in the historic time period, just like we see both Greek and Persian social customs presented in The Persian Boy. As Renault said herself, "Universals of human feeling ... thread their way among accidents of custom and belief which, like rocks and shallows, direct their course but do not change their essence" ("Critical Essays"). By this she means that even customs and beliefs specific to one culture or one time period are based on universal human feelings, and if we understand these universals, we see how these universals directed history. She specifically wrote The Persian Boy with the view of analyzing Alexander III to explain the reasons behind his greatness and the reasons for his army's loyalty. More importantly, she offers her own view, or perspective, concerning why Alexander invaded Persia. It has been argued that Renault presents the idea that Alexander wanted to conquer Persia with the object of uniting the Greeks and the Persians; he wanted to unite them due to his love for his vizier Bagoas, a former Persian slave ("The Persian Boy").
Throughout the novel, Renault builds and captures the relationship between Bagoas and Alexander. While Bagoas was given to Alexander as a slave by the Persian court as a peace offering, their relationship soon buds into the type of friendship Greeks valued between equals and even the sexual relationship between mentors and mentees that Greeks also valued, the what the Greeks saw as the highest form of love, showing us Renault's viewpoint that Bagoas influenced Alexander's drive to conquer Persia. More specific evidence of Bagoas' influence on Alexander is the fact that Alexander makes it clear he is not just interested in conquering the Persians but in creating a Greek-Persian dynasty. Alexander makes his intentions of a Greek-Persian dynasty clear by marrying King Darius's daughter, as King Darius was king of Persia. He also gave her younger sister as a bride to Hephaistion, his devoted friend and lover, and married "eighty Greek nobles to Persian ladies" (eNotes, "Characters"). Hence, according to Renault's perspective, all of these marriages indicate that Alexander wasn't simply interested in conquering Persia to gain new wealth and territory; he wanted to see the Greek and Persian cultures merged rather than at constant war with each other.