Gongduzi asks why people differ morally. Mencius distinguishes the thinking moral heart (greater part) from passive, easily misled senses. Prioritizing the heart secures virtue and makes one noble, while following senses makes a petty person.
Mencius uses a bent finger metaphor to criticize misplaced values. People travel far to fix minor physical flaws yet ignore their flawed inner moral minds. Such blindness to spiritual priorities is called failing to distinguish what truly matters.