We all have an idea of goodness, but there is no objective measure of good. Each of us measures goodness in our own way. One person may think something good while another may think the same thing bad.
I started out believing people are naturally good, but drifted to a more neutral notion as I aged. Here's why:
Self-preservation is the first law of nature. Before humans reached the cave-man state they did what they had to do to survive. They existed like other animals. They killed for food and they killed those who threatened them. For them, killing was not a moral issue it was a matter of survival.
It is likely that these beings existed in herds, that they hunted and sheltered together, instinctively. If so, they might have lived like what we refer to as cave-men. However, those beings did not become "human" until they began to change their animalistic behavior. The ability to make such a change defines what we call humans.
Assuming cave-men lived in groups, it is reasonable to imagine that the most effective survivors of the group were the strongest members. We can also imagine that the strongest could and did take from the weakest. It is also likely the weaker took what they could from the stronger, even if it was only "leavings", to satisfy their needs.
But, need is relative. It depends on many factors. In the case of cave-men, it depended on the availability of food, an individual's size and/or appetite, the need to provide for mates and offspring, need to store reserves, and many other factors. It is not hard to imagine that, however primeval, different members of the group had different needs.
When these beings started to change their animalistic behavior, when they began to "think", there is a high likelihood that their thoughts related to their needs. At some point, those thoughts expanded to include opinions or judgments about the needs of other individuals in the group. The concepts of "good" and "bad" must have originated in this way.
At some point in the existence of cave-men, the weaker members of the community recognized that, since they did not have the strength to take from the stronger members by themselves, they needed the help of others if they were to survive. It would not have been difficult for the weaker members to recognize other members of the group who also suffered by their weakness. In some way, these weaker members combined to limit the domination of the stronger. That was the beginning of "civilization".
What is not stated, but must be recognized, is that the stronger members were members of the same group. They did not stand idly by and allow the weaker members to take from them. They participated in the formation of a solution. They used their strength to protect as much of what was "theirs" as they could. This laid the foundation for the concept of "ownership", and, by extension, the concept of "greed". Ownership was claimed by the strong and the attribution of greed was laid by the weak. This is the most important, but least acknowledged, aspect of the relationships which led to the origin and structure of civilization.
If this is a reasonable estimate of the origin of civilization, several things stand out:
1) Morality, or the concept of "good and bad", can not exist in the absence of intelligent thought. The squirrel, when he stores nuts for the winter, does not ask himself if he'd be wrong to store one more. If he finds another and feels the need for it, he takes it. For animals, there is no issue of good or bad, and the concept of "greed" does not exist. A moral sense is a mark of intelligence.
2) The driving force for the organization of society is the need to restrain the strongest members of the group. If the weaker members of the group do not feel threatened by the stronger, there is no need to organize.
3) The threat the weaker members of the original society felt had to result from deprivation of the resources needed for existence (probably food). If the stronger were perceived as taking more than they needed while the weaker suffered, that condition must have been characterized as "bad".
4) The mechanism society uses to restrict bad behavior is force. By definition, a weaker member can not control a stronger one. But, several weaker members, in unison, have enough power to control even the strongest. In this sense, civilization is a banding together of the members of a group to gain the strength needed to control members exhibiting "bad" behavior.
5) When discussing these relationships, we tend to use sophisticated terms to differentiate forms of undesirable behavior. Thus, we call the taking of more than one needs "greed". This tempts us to say civilization developed to limit greed. It is more likely the initial banding together mentioned above was to ensure the survival of the weaker members of the group rather than to penalize the stronger.
6) The role of civilization as a means of controlling excessive strength or power evolved over time. As the goods available for consumption expanded beyond rudimentary food, clothing and shelter, we see ample evidence that the more powerful acquired the surplus goods first. At the same time, they increased the sophistication of the ways they exercised their power to control what they considered "theirs". Reactively, the less powerful slowly developed ways to force broader distribution of the surplus goods. That process continues today.
Looked at this way, the concepts of good and bad can not exist for a single individual. They can only exist in terms of others. I was wrong to believe that humans are naturally good. At birth, they are neither. It's true some children are born with what is called a "bad" nature, but that is a judgment rendered by others. The infant, itself, has no concept of "good" or "bad".
For each of us, the idea of good and bad grows as we develop. Initially, we see those who gratify our wishes as good and those who deny us what we want as bad. But we soon realize good and bad are much more complex than that. We exist in a constant and ever-changing mixture of good and bad, starting with our parents who supply our needs (good) and control us (bad). The choices we make flow from our understanding of that mixture, influenced by our individual characteristics. The more powerful among us may consider actions good that are abhorrent to the less powerful, but they are neither good nor bad unless they affect others and their goodness or badness depend how they affect others.
That, it seems to me, is the essence of good and bad. It is also a fairly obvious statement of the human condition. While the foregoing was written in a search for the origin and nature of goodness, it painted a picture of the weaker members of the human race forcing civilized behavior on the stronger and the stronger members impeding the civilizing efforts of their weaker brethren as well as they could. I started out trying to derive a basis for believing that humans are naturally "good", a personal bias I wanted to justify. I failed. Instead, I found a basis for understanding why we can't trust our leaders.
But that seems to create a paradox: We must have leaders, and leaders, by their nature, must lead. We are properly taught from childhood to respect and revere our leaders. How can we square that with the notion that "we can't trust our leaders"? We can only do so when we recognize that there is a difference between "trust" and "blind trust". Even those who followed Alexander learned to put bounds on his ambition.
It has ever been so.