That no longer holds if one can be cruel without being seen for what one is--then it is one's rational self-interest to screw whatever poor sod's unfortunate enough to need one's help.
Helping those in need is not morally required
Things that are required incur a penalty--most often in the form of reprobation--if not done, correct? Do we not (justly) call a man cruel who gives no aid to a starving child or a person drowning in a river, especially when such aid is easily within his power?
it is in a person's rational self interest to show the same empathy for others, that one would like to experience from others.
That no longer holds if one can be cruel without being seen for what one is--then it is one's rational self-interest to screw whatever poor sod's unfortunate enough to need one's help.
Not so. It's not about who sees, or who knows. It's about the world in which one would like to live.
Do people only pick up trash in a park when there is someone to see? Why, then, do people do it? They do it because they know that if no one ever picks up the trash, their enjoyment of the park will be diminished. So they pick up trash, based on the rationally-justified assumption that the more people there are who voluntarily pick up trash in parks, the greater the chance that yet other people will come to realize that picking up trash is in their rational-self interest.
Uncoerced cooperation, empathy and compassion breeds more of the same--unlike the coerced variety.
The world is much more likely to resemble the way we would like it to be, if we do things that will move the state of the world in that direction. If you want to establish a social habit in the population of picking up trash, your most effective course of action is to pick up trash yourself.
Helping those in need is not morally required
Things that are required incur a penalty--most often in the form of reprobation--if not done, correct? Do we not (justly) call a man cruel who gives no aid to a starving child or a person drowning in a river, especially when such aid is easily within his power?
'A implies B' does not imply that 'B implies A.'
If the fundamental principle of morality is that one must never do anything that someone else doesn't like, then it is just as useless as a system of logic where any propostion that can be proven to be true can also be proven to be false.