Mencius
Mencius or Mèngzǐ in Pinyin is one of the Four Books and written by Chinese philosopher Mencius. The book, like the Analects of Confucius, is a collection of dialogues, debates and stories where Mencius talks about how he thinks ethics, morals and more should be handled. The book itself is divided into 7 books, each divided into two parts, A and B.
Concepts
One of the main things Mencius believes is that every human is inherently good. He compares one's morality to a sprout, it's natural but it needs cultivation to flourish/grow. This can be achieved with educating oneself and self-reflection.
Mandate of Heaven
Mencius, like the Doctrine of the Mean, talk about the Mandate of Heaven. The text says that if a king is tyrannical or unjust that he has lost the Mandate from Heaven and that the people have the right to revolt against the king (or ruler). Mencius also believed in fair taxes and equal land distribution for stability.
Passages
The following exerpt is from Book 2A:6, The Child and the Well
"Suppose a man were, all of a sudden, to see a young child on the verge of falling into a well. He would certainly be moved to compassion—not because he wanted to gain friendship with the child’s parents, nor to seek praise from neighbors and friends, nor because he disliked the child’s cries. From this we can see that one who lacks a heart of compassion is not human."
Humans feel empathy when seeing suffering, in this case suffering being the young child. Mencius is saying that morality is natural, not something that has to be taught.
The following exerpt is from Book 6A:1-6, Mencius' debate with Gaozi, a rival philospoher
Gaozi: "Human nature is like swirling water: open a passage for it in the east, and it will flow east; open a passage for it in the west, and it will flow west. Human nature is neither good nor bad, just as water does not prefer east or west."
Gaozi's point is that morality is shaped by external factors, like the flow of water. Humans are not inherently good, rather their morality is dependent on their surroundings.
Mencius: "Water certainly does not prefer east or west, but does it have no preference for up or down? The goodness of human nature is like water’s tendency to flow downward. All people have this tendency to be good, just as all water flows downward. Now, by striking water you may splash it upward, but this is not water’s nature—it is forced. Likewise, when people become cruel, it is not their nature but their circumstances that cause it."
Mencius rebuts Gaozi by saying that morality is not dictated by external factors but it being something natural or inherent. Evil, or cruelity is caused by as Mencius says the circumstances that cause it.