Final answer:
According to Nagel's account, the fact that it would be morally wrong for you to steal someone's umbrella gives you a reason not to steal it because we wouldn't like it if someone did it to us, so we are motivated to not do it to someone else. Similarly, the fact that some words can cause harm and we wouldn't want harmful words used on us gives us the moral motivation to avoid using them in a harmful way.
Step-by-step explanation:
According to Nagel's account, the fact that it would be morally wrong for you to steal someone's umbrella gives you a reason not to steal it because we wouldn't like it if someone did it to us, so we are motivated to not do it to someone else. This is based on the principle of reciprocity or the Golden Rule, which states that we should treat others as we would like to be treated.
Applying this principle to the use of harmful words, if we wouldn't want harmful words used on us, then we have moral motivation to avoid using them in a harmful way. Just as stealing someone's umbrella would be morally wrong because we wouldn't want our umbrella stolen, using harmful words on someone would also be morally wrong because we wouldn't want harmful words used on us.
In conclusion, Nagel's account provides a compelling explanation for why the fact that it would be morally wrong for you to steal someone's umbrella gives you a reason not to steal it. Similarly, the fact that some words can cause harm and we wouldn't want harmful words used on us gives us the moral motivation to avoid using them in a harmful way.