徐广联老师著《大学英语语法讲座与测试》中提到虚拟语气用在非真实条件句中，非真实条件句包括虚拟条件句，推测条件句和错综时间条件句等。书中例举了这样两个例子：

与将来事实相反的虚拟条件句：If it were to snow tomorrow, I should (would) stay at home.

推测条件句：If I were to see him, I would speak to him about it.

疑问：我就分不清这两句哪个是虚拟条件句，哪个是推测条件句，感觉这两句结构一模一样，如何区分呀？语法书上（表示与将来相反的虚拟条件句）和（推测条件句）结构相同，都是如下结构：从句为一般过去式 / were to do / should+原型，主句用 would+动词原形，一模一样，看不出有何区别？

【答】根本不用细分，不用区别，其实都一样，不要把简单的问题搞复杂了。都是虚拟语气，都是表示“将来不可能发生或实现”的虚拟语气，谈不上“相反”二字，只是可能性极小，这属于表述不当，“下雪天”的反义应是“烈日炎炎的三伏天”，明天可能有吗？所以，即便是虚拟语气，也不建议使用“相反”二字。以下几种表达都正确：

If it were to snow tomorrow, I would stay at home.

If it should snow tomorrow, I would stay at home.

If it snowed tomorrow, I would stay at home.

If I were to see him, I would speak to him about it.

If I should see him, I would speak to him about it.

If I saw him, I would speak to him about it.