6 ideas
They do this because they are programmed to, not because they decided to. The act looks heroic, but it is not moral, because morality begins only where a creature could have done otherwise and must decide which way to act.
Most actions are driven by orders from others, by customs we inherited, or by passing whims. Each can be a reasonable guide. None of them excuses you from asking whether this particular action is what you actually want, and ethics is the habit of asking that question.
The core rule is 'do what you want.' This is not a license for impulse. It is a demand to find out what you really want across your whole life, beneath momentary cravings. Because no one else can answer that for you, the rule gives you no external authority to hide behind, which makes it harder than obedience.
A moral 'imbecile' is not unintelligent. It is someone who limps in how they want things. The imbecile may want nothing, want everything at once, want contradictory things, or give up what they deeply want for an immediate appetite. Esau selling his birthright for a bowl of lentils is the model case of trading what matters for what is near.
Charles Foster Kane gathers enormous wealth, power, and possessions. He dies whispering the name of a childhood sled that stands for lost affection. The story shows that things cannot provide the good life. What we most need is to be treated as a person by other people, and we can get that only by treating them as persons in return.
Being free does not mean you can make anything happen. Circumstances, other people, and chance limit what occurs. Freedom means you can always choose how to respond within those limits. Hector cannot choose whether Achilles is stronger, but he can choose to face him rather than flee.