It is (almost) always wrong to be cruel, as it (almost) always favors such emotions as will trip you into deeds you’ll regret.
To be good is to do and want what is truly in your interest, in the long run and all things considered.
To be good is to do and want what is truly in your interest, in the long run and all things considered. How could it not be so?
It should be pointed out, however, that we rarely consider what is truly in our interest, but rather settle too quickly for what we desire in the immediate, what someone else wants for us, or what our feelings of revenge, pride or even love are pushing us towards. We also usually fail to think in the long run (which always begins now): we settle upon that which will make us happy today but miserable tomorrow. Nor do we very often consider all things, but like a poor chess player, we give up thinking through our move half-way when our minds pretend to tire, hoping our lazyness will be rewarded with luck.
Many of those things to consider involve other people, animals and situations, and it is certainly in our interest to ensure those are happy whose misery will make us sad. Here too we must consider how our deed might cascade through many iterations before it comes home to roost.
If, however, we do carefully examine our own interest, and act accordingly, we will really be good, for we will be doing our best to the greatest extent and produce the happiest outcomes possible.
Do not ask: Unde malum? but: Unde malum atque bonum?
There is no good reason to assume that the world is good and then ask how evil came to it. The greater mytery is whence our concepts of good and evil came from. One simply explanation is evolutionary: one day, someone came up with the word “good” and said to her friend, pointing at a berry: “good!” and pointing at another, poisonous one: “bad!”. Humans suddenly had a means of structuring their social interactions, of getting one another to do things by talking to them. The invention of the words “good” and “bad” or “evil” was a revolution, like the invention of agriculture or electric power.