Charles B. answered 08/12/20
English Tutor Extraordinaire!
As the narrator, Nick Carraway is the filter by which we see and evaluate all of the characters in Gatsby. So before we can answer your question, we must first assess whether NIck himself is a reliable narrator. That is, can we rely on NIck not to have an axe to grind in how he represents the characters? If we conclude that Nick is a reliable narrator, i.e., does not have any particular narrative agenda, then Tom, Daisy and Jordan each function as a "foil" to one aspect of Jay's character. If, on the other hand, we conclude that Nick may have his own peculair agenda in idolizing Gatsby, i.e., is an "unreliable narrator," why then we see that Tom, Daisy and Jordan .-- and Gatsby himself -- are foils for Nick's character.
Sorry to sound so cryptic but your assessment of Nick's "reliability" must serve as your starting point.
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