In modern times we separate philosophy from science, but in earlier times the kinds of studies we now call science were called "natural philosophy," and Mencius was basically a natural philosopher. His work led to the same general kind of knowledge that Lorenz learned about ducks and other animals. Mencius asked: what kinds of things do people do that keep families and communities working well, what kinds of things do they do that harm families and communities, and why do they do these thing?
Mencius said that we do not need to teach people to love the taste of good food. The feeling we have for fine cooking is natural. Similarly, he said, we have other natural feelings that are good gifts that we are all born with. We cannot really get rid of these gifts except by destroying ourselves, but we can allow them to be covered over so that they do not work right. It is a little like the way humans cannot just take off their noses and throw them away, but they can put plugs in their nostrils and spoil their ability to smell things. So it is important that humans not do anything that would prevent their four gifts from working well. It is too bad that people often let their four gifts get messed up. When humans are well nurtured and are protected from negative forces, then they will be good of their own free will.
The virtues or powers that humans have are things that they get directly from Heaven. These same things are in Heaven. When people do bad things, it is because their other parts have taken control away from their virtues/powers. Mencius gives a wonderful story that is called Ox Mountain as proof.
The Chinese word for what has been called "gifts" above is 德 dé. It is a cognate of a word that means "to get," so one way of explaining it is to say that a dé is something that we get from Heaven. It means "virtue," but only in the sense that it is the power to do something. ("Virtue" has this meaning in English, too.) Humans have four virtues or powers. Here are their Chinese names, a translation of each, and an explanation of each:
Human beings might be able to live perfect lives if they had only these four kinds of motivations or emotional reactions to the world, but they have many other motivations. They include fear, anger, greed for wealth and power, sex, etc. Humans very easily learn that they can satisfy these drives more easily if they ignore the inputs from their virtues. For instance, a child who is large for his age may easily learn that he can take by force whatever he wants from other children his age.
Human beings are born with the four powers that would keep them from doing bad things, and they are also born with the many drives or motivations that can lead them to do bad things to satisfy these needs. So what determines who will be good and who will be bad?
Mencius observed that humans depend on one more important mental function. He called it the 志 Zhì, which can sometimes be translated as "aspirations," but which in the case of Mencius is what we would call the will. Something has to decide what to do when the ethical impulses, the moral feelings, of what Mencius called the "four virtues," conflict with the ordinary impulses that are involved with hunger, sex, aggression, fear, etc. The part of humans that balances things and makes decisions is the zhì.
For Mencius, if an individual is functioning well, then his or her will can strike a healthy balance among all the impulses and can keep the virtues from being swamped by the ordinary desires. If a person's will is not in control, then that person may do damage to himself or herself, or to other people. So it is important while growing up to learn how to keep the zhì from getting taken over by other forces—or by other people.
The individual has a free-will choice about whether to integrate (put together so they will not fight each other) all his impulses and also his intellect, or to give up and just act on whatever impulse is being felt at the moment. So for Mencius the best path for a human being is to plan and to act to make himself or herself well balanced, integrated (not in a fight with himself or herself and wanting to do both one thing and its opposite), and so a useful person to society.
Somebody who operates at the very high end of the moral scale by "having his act together" is called a 君子 jūn zǐ, or "morally noble man." 孟子曰：「人之所以異於禽獸者幾希！庶民去之，君子存之。舜明於庶物，
察於人倫，由仁義行，非行仁義也。」
Mencius said: "That by which humans differ from the birds and the beasts is extremely small. Ordinary people get rid of it, but the morally noble man keeps it safe. [The sage emperor] Shun clearly saw the many creatures, and he made a close examination of human social relationships. His actions came out of his benevolence and his sense of duty. He did not act out [a phony] benevolence and sense of duty."
So a jūn zǐ is somebody who has managed to hold onto the gifts that Heaven has given him, the gifts that can make humans act with benevolence, be led by a sense of duty, want to act in ways that will keep good relations with others, and try to aid and protect people who are being treated unfairly. To be a real jūn zǐ, the person has to have these true feelings and to act on them. It is not enough just to act as though one has these feelings.
According to Mencius, anyone can choose become a morally noble man. All it would take would be to really make that decision and then do it. Mencius talked about Yan Yuan, who was the favorite disciple of Confucius:
顏淵曰：『舜何人也；予何人也。有為者亦若是！』
Yan Yuan said: "What kind of a man was Shun? What kind of a man am I? All it takes to be like him is to do it."
Of course Mencius realized that "just doing it" is much harder than talking about it. One has to keep watching oneself all the time.
One goal that Mencius had was to grow what he called an "unmovable mind." By those words he meant a mind that could not be knocked around by being hit from the outside. An "unmovable mind" is guarded against doing the wrong thing because one is angry, afraid, etc. Anything that can pull or push from the outside and make us go out of control could cause harm, but Mencius says that if the will and the four virtues/powers are well integrated, if the person is "really together," then these outside forces cannot take over control.
Every culture and every society has developed ways to prevent children from getting into too much trouble. Even in a single community people may used several different strategies for getting and keeping control over their children. One way of controlling children is to beat them when they do things that the parents do not want them to do. Another way of controlling children is to make them feel guilty and expect to be severely punished because they are bad humans. A third way is to make children feel shame and expect people to laugh at them and then turn away from them. Method number four is to explain to children the likely results of their actions. "If you pull the dog's ears he will bite you." Many parents the world over use more than one of these methods, and they may use all of them from time to time.
The Chinese culture has another method that may not be well known and may be rarely practiced in other places—calling forth the use of the child's own virtue/power. When a child does something hurtful to someone else, instead of telling the child how bad he or she is the parents may say something like: "Just now we saw you take the eggs out of the sparrow's nest. We know that you are a good person at heart. So we wonder whether you thought about how the mother sparrow will feel when she comes back and finds her children gone. Would you like to put the eggs back now while they are still warm? The mother sparrow will be coming back soon."