"Then why does he give discourses"?

那他为什么要讲学？

Her eye discourses; I will answer it.

她的眼睛在说话；我要回答她。

I must admit that is not common in public discourses.

我承认在公开演讲的场合那是件不寻常的事情。

Eg. It is said that his discourses were very soul-moving.

据说他的讲道词是很能动人心灵的。

Discourses on Livy. Book 2. Introduction, and chapters 1-2.

马基·维里，《李维罗马史疏义》第二卷引言，1 - 2章。