【问】 (1) I've loved you as if you were my son.
 (2) It looks as if it is going to rain.
 as if用虚拟语气与用陈述语气有无区别?
 【答】 一般而论，如果as if从句所表达的内容完全与实际情况相反或者纯粹是一种假设时，通常使用虚拟语气。句(1)含有“你并不是我的儿子”这个含义。请分析下面各例：
 1. He acts as if he knew you.(具有“他并不认识你”的含义)
 看他的样子似乎认识你似的。
 2. She looks as if she were angry.(具有“她并没有真的生气”的含义)
 看她的表情，她好象生气了似的。
 3. He walks as if he were drunk.(说话人认为“他并没有喝醉”)
 他走路的样子好像是喝醉了似的。
 4. I remember the whole thing as if it happened yesterday. (Wilde)
 我记得整个事情，就好象它是昨天发生的似的。
 5. You look as if you didn't care. (Galsworthy)
 你看上去好象是不在乎似的。(说话人认为“他事实上是很在乎的”)
 6. As if this were not enough to reduce you to tears，your husband arrives，unexpectedlybringing three guests to dinner. (New Concept English，Book 3，L. 33)
 似乎这一切还不足以使你气恼得流泪似的，这时你丈夫回来了，出乎意料地带着三个客人来吃饭。
 如果as if (though)从句所表达的内容被看作是事实或者有可能是真实的，就要使用陈述语气。
 1. He walks as if he is drunk.
 他走路好象喝醉了似的。
 2. It looks as if she is in love again. (RWRT)
 看上去好像她又坠入情网了。
 3. It looks as though we shall have to do the work ourselves. (Wood)
 看来我们好象不得不自己来做这项工作了。
 4. It seems as if we shall have to walk. (AEP)
 看来好象我们不得不走着去了。
 5. This meat tastes as if it has already gone bad. (AEP)
 这肉尝起来好象坏了。
 6. The milk smells as if it is sour. (AEP)
 牛奶闻起来好象酸了。
 7. It seems as if you are the first one here. (DAI)
 看来你好象是最先到这儿的。
 8. It sounds as if somebody is knocking at the door.
 听起来好象有人在敲门。
 9. He looks as if he’s tired.
 他看起来好象累了。
 10. He looks as if he’s getting better.
 他看上去好象好多了。
 11. It seems as if the weather is improving.
 天气好象转好了。
 在你所提问的句(2)中，as if从句使用陈述语气，是因为说话人认为“真的要下雨”。因此之故，RWRT作者们认为应将下列句中的as if snow were coming改为as if snow was com-ing：
 The light，though late now，was sharp，as if snow were coming on...behind that freezingiron leaf he watched the slice of cold evening，and pulled his coat across his chest. (RWRT)
 尽管当时已经迟了，光线还很分明，似乎接着就要下雪了……在那冻结得铁一般的叶子后面，他看着这一片寒冷的夜晚，并把外套拉过胸部。(译文引自《英语准确用词词典》)
 但是，也有特殊的情况：as if从句使用陈述语气或使用虚拟语气，其意义并没有什么差别。这主要是因为从上下文或句义可以明显地看出as if从句所表达的内容是非真实的。
 1. She treats me as if a stranger. (CGEL)(这两个句子都意味着“我并不是一个陌生人”)
 她对待我的态度就好象我是个陌生人似的。
 2. There he is to the life，looking as if at any moment he will slowly open those large greyheavy lidded eyes，stare at us solemnly for a minute，and then declare that“really hehasn’t the least idea. ”
 这是写生画出来的他的肖像，看上去现在还好象他会慢慢地睁开那大而灰色的，眼皮重重地垂下着的两眼，严肃地望着我们，一会儿之后，就会说出，“我真是一点也不知道呀。”(译文引自钱歌川《英文疑难详解续篇》，P.162)
 (参见as if he{knew knows)