copy something I wrote several years ago:
Jealousy stems from association and identity.
People are only jealous of other people when they feel that the
situation is similar: "I could be like that." If there is no
connection, if the other person's situation is completely foreign,
then there is no jealosy because there is no opportunity to imagine
oneself in the other's position.
Therefore, it is in the interests of the ruling class to mentally
distance themselves from the lower classes as much as possible.
Proles are only jealous when they start to think that they could be
like the rulers.
The true danger is when people start to think, "I am like him, but
somehow he is in a better position than me."
I don't have much to add to this; I still agree with it and still
think it is well-written. (This happens less than you might think; I
have grown a lot in the past three years.) But it can be expanded.
This effect is common to many emotions. People have very strongly
felt beliefs about other human beings, but it is frighteningly easy to
make them consider someone 'non-human' and therefore outside all moral
thoughts and comparisons.