This is the tradition's central internal argument and it was never resolved so much as decided. Mencius holds that human nature is good: everyone possesses four sprouts — compassion, shame, deference and the sense of right and wrong — and the proof offered is that anyone who suddenly sees a child about to fall into a well feels alarm before any calculation of advantage or reputation enters. Cultivation is therefore growth, and the metaphor is agricultural. Xunzi holds the opposite: nature is what you are born with, and it is greedy, envious and disorderly; goodness is deliberate artifice, the product of teachers and ritual, and his metaphors are the steaming and bending of warped wood and the grinding of a blunt blade. Both agree everyone can become a sage; they disagree entirely about what that requires. Mencius became orthodoxy from the Song onward, and the result is a tradition officially committed to innate goodness while operating an educational apparatus that makes far more sense on Xunzi's premises.