弘明集 9.74

9.74

答曰。有禽焉有獸焉。飛走之別也。有人焉有鬼焉。幽明之別也。人滅而為鬼。鬼滅而為人。則吾未知也。

[Fan Zhen] replied: There are birds and there are beasts—this is the distinction between flying and running. There are humans and there are ghosts—this is the distinction between the dark and the bright. But that humans perish to become ghosts, and ghosts perish to become humans—this I do not know.