for가 접속사로 쓰이는 꼴은

문두에는 못 쓰이고 문중에서 , for

가령

we listened eagerly, for he brought news of our families
이런식으로 밖에 쓰이지 않는다고 배웠는데 웬걸 for 가 저렇게 쓰였길래 궁금해서 질문을 해봅니다.
저 for를 앞의 문장과 내용상 이어졌기 때문에 저렇게 써도 무관한 것인가요?
아니면 제가 접속사 for에 대해서 잘 못 알고 있는건가요??

on this ground, actions in conformity with virtue must be intrinsically pleasant. and certainly they are good as well as noble, and both in the highest degree, if the judgment of the good man is any criterion; for he will judge them as we have said.
it, follows, therefore, that happiness is at onece the best and noblest and pleasantest of thing. for our best acrivities possess all of these attributes.