Question

How does the ghost undermine the narrator's faith in his ability to write ghost stories???

Answer 1

he told him that it was he (the ghost) who used to put ideas in his mind and he was able to write stories but nowadays they were on striking so he was not able to get any ideas...... hope it helps you

Answer 2

The ghost make him aware of the fact that till now whatever stories he has written it was not his own. Instead it was the ghost community who were helping him to write.