请教曹老师：

“That is what Mr. Hilton Cubitt, of Riding Thorpe Manor, Norfolk, is very anxious to know. 

This little conundrum came by the first post, and he was to follow by the next train. 

There’s a ring at the bell, Watson. I should not be very much surprised if this were he.”

这正是希尔顿·丘比特先生急着想搞清楚的问题，他住在诺福克郡赖丁索普庄园。

这个小谜团是今天首班邮车送来的，他本人准备搭乘下一班火车前来。

门铃响了，华生。来人如果是他，我一点也不会感到吃惊。”

节选福尔摩斯《The Adventure of the Dancing Man》。

分析这一句： I should not be very much surprised if this were he.

这里为什么要用虚拟语气should, were? 如果用陈述句

 I SHALL not be very much surprised if this IS he. 意义有何不同？

虚拟语气反映了说话的人的心理想法，故事中，是福尔摩斯当时说的。

我就说想请教老师：

福尔摩斯说 I SHOULD not be very much surprised if this WERE he.

和如果福尔摩斯这样说：

I SHALL not be very much surprised if this IS he.

那么，对于福尔摩斯，这二种说法，内心想法究竟有何不同？