Answer:
People's thoughtlessness about each others' suffering.
Explanation:
In this passage, the main idea that Wiesel conveys is that people can often be thoughtless when it comes to the suffering of others. In the text, we learn that Wiesel talks to an elegant Parisian lady in order to convince her not to throw coins in the water. She is unaware of the fact that the coins, which make no difference to her, are very important for poor children, whose suffering might be alleviated by having the coins.
