Improper workmanship would produce bad results; good workmanship, on the other hand, would produce good results.

In plain words, the nature of man at birth is neither good nor bad; and what it becomes afterwards depends entirely upon what influences have been brought to bear and in what surroundings it has come to maturity.

Mencius met this argument by showing that in the process of extracting cups and bowls from a block of wood, the wood as a block is destroyed, and he pointed out that, according to such reasoning, man's nature would also be destroyed in the process of getting righteousness out of it.
Again, Kao maintained that man's nature has as little concern with good or evil as water has with east or west; for water will flow indifferently either one way or the other, according to the conditions in each case.

If there is freedom on the east, it will flow east; if there is freedom on the west, it will flow west; and so with human nature, which will move similarly in the direction of either good or evil.

In reply, Mencius freely admitted that water would flow either east or west; but he asked if it would flow indifferently up or down.
He then declared that the bent of human nature towards good is precisely like the tendency of water to flow down and not up.