Final answer:
Indirect characterization of Gatsby in 'The Great Gatsby' is predominantly accomplished through the perspectives and reactions of other characters, especially via the narrator Nick Carraway, and Gatsby's own dialogue and actions as interpreted within the text.
Step-by-step explanation:
Gatsby is indirectly characterized in The Great Gatsby primarily through the observations and opinions of other characters, notably through the flawed perspective of Nick Carraway, the narrator. Nick's insights and the way he perceives Gatsby provide us with a filter through which to see Gatsby's actions and hear his words. Fitzgerald also uses Gatsby's own thoughts and feelings, as deduced through his dialogue and actions, to shape our understanding of his complex character. While we don't know all of Gatsby's secrets, the way other characters interact with him and describe him adds layers to our interpretation of his persona, making him both enigmatic and relatable in the context of the American Dream and the 1920s era.