Introverted Intuition (Ni): Atticus has great foresight when it comes to both the consequences of his actions and of other people’s. He predicts danger to Mr. Robinson and heads to the prison to prevent it. He’s aware of the trial’s eventual outcome long before it presents itself, but goes through with it regardless because of his idealism. Atticus’s long-term vision extends well beyond his own lifetime and into a future in which America is a land of equality, and he proceeds to live the ideals of that future rather than fitting into present moral guidelines.
Extraverted Thinking (Te): Atticus bases his entire court defines on empirical evidence, rather than simply assuming that witnesses will tell the truth. He finds one piece of truth (that the person who beat the girl was left handed) and proceeded to compare every other piece of evidence with that to see whether it checked out. (this isn’t something a Ti user does). Atticus is generally calm under pressure, articulate and measured in his words, and places high value on education (both for himself and for his children).
Introverted Feeling (Fi): Atticus’s sense of right and wrong is different from the norm in his community. He doesn’t care what anyone else things of his decisions, but would rather do what is right in his own heart than be accepted by others. When he says that if he didn’t take Robinson’s case he couldn’t hold his head up in town, it’s not because he’s worried about harmony or social morality. What he’s choosing to do there actually goes strictly against the norms of his community. It’s something that he knows is right within himself. Yet, Atticus is mature enough in his F function that he makes an effort to keep the peace within his community, by showing kindness to all without violating his principles.
Extroverted Sensing (Se): Atticus is “too old” to play tackle football, “too old” to do anything he doesn’t want to do. Evidently he’s just not into physical exertion. Yet, he’s secretly the best guns-man in town. He loves nature and spends a great deal of time sitting on his porch enjoying it. He cares about his appearance enough to consistently go about well dressed. Most of his arguments are backed up with physical, empirical evidence.
Atticus Finch is canonically accepted as an INFJ simply because he cares about harmony. However, his sense of morality is entirely Fi-based. Just because somebody cares about other people does not make them an Fe user. Atticus is an INTJ with an extremely well developed Fi, much like Ender Wiggin and Bruce Wayne.