Logic definition of ethics
Ethics is based on a person’s actions and how it positively or negatively affects the person performing the action and the people affected by that action. Empathy is considered as the base of ethical conduct, as it is able to be applied consistently across individuals through autonomy; the wishes (freedom) of the people involved is therefore considered.
Ultimately freedom is the main thing that is attempted to be maintained in ethical practice.
Freedom is when a person is under no hindrance or control in terms of their intentions or will.
Acting ethically will therefore be to act without causing the freedom lost in others to outweigh the freedom you are exercising in order to perform that action.
Also, because the only way to know something is ethical or unethical is to have the physical representation of memory in the brain that suggests so, this is also taken into account. If an ethics system is isolated, there is no ethical value assigned to any action because no-one knows about it. Some examples:
Two people who are unknown by anyone else (no-one is expecting to see them, or has any wishes for them) are somewhere no person can observe them. One murders the other. In this case, while it is likely immoral that the murderer did what they did, there is no ethical value to be assigned as ethics is based on the effects of actions. Morality is the value an individual places on what memories of events they have. Ethics is the same, where the value is established systematically and the effects of the actions on all involved are considered.
In other words:
Acting ethically is to act without causing (memories of) freedom lost in others to outweigh the freedom you are (perceived to be) exercising in order to perform that action.
Murder therefore is unethical as the person’s freedom to kill the person is not as great as the other person’s freedom to remain living, and the will of others for them to remain living.
Complete destruction of the human race is unethical only until there are no more people able to remember the events that make it unethical.
The murder of someone who has no links to any other person is not ethical, but is not assigned the ‘unethical’ tag either, as it is a matter of morality after they are gone.