Though he has had ups and downs,I believed all along that he

Though he has had ups and downs,I believed all along that he would succeed someday.语法讲解.
为什么后半句要用过去式（虚拟语气?英语菜鸟求解啊.

诸如 believe, think, expect, suppose, imagine, know, realize 一类表示内心活动的动词,在表述既往事实的时候,都应该用过去时态,如：

Sorry, I didn’t know you were having a meeting, so I’ve dropped in. （对不起,不知道你们正开会,因此我就进来了.）

例句中,由于“不知道”是发生在“知道开会并进入”以前,所以需要用didn’t know 来表述,宾语从句中的时态也需要与主句的时态保持一致,故而用了过去进行时were having.

本句也是如此,“一直认为”是发生在“现在不认为”的以前,因此主从句就需要用I believed all along that he would succeed someday,意思是“我原来一直认为他总有一天是会取得成功的”,言外之意是“结果他现在却是沉浮不定”.

当然,如果在主句中用这类动词的过去式表示“原本以为”,那么整个主从句表达的是一种现在已经不存在的个人见解,因此可以把它归属于虚拟语气.