# How can you tell the difference between subjunctive and contrary to fact?

My GMAT book, GMAT Ultimate Grammar, has different sentence structures for present subjunctive form and present contrary to fact form. However, they both seem identical to me because in the examples given of each form, they both talk about something that isn't true. The book gives an example of each:

• Subjunctive: She would rather that the plane leave early in the morning.
• Contrary to fact: Debby would rather that her boyfriend spent Friday nights with her.

After stating the contrary to fact example, the book says that the sentence implies that Debby's boyfriend does not spend Fridays with her. However, couldn't you argue that their example for the subjunctive case implies that the plane will not leave early, making it contrary to fact?

• The actual difference in the above examples is the tense. "Subjunctive" uses the bare infinitive. "Contrary to fact", often called "irrealis", uses the past tense (except for the verb to be, in which case it probably uses were). For these two examples, the difference is leave/left and spend/spent. Sep 22, 2017 at 0:17
• @PeterShor That's exactly right. I like seeing this clear-cut example here between the two cases using normal verbs like leave/left and spend/spent so that we don't have to resort to yet another be/were contrast that might risk confusing folks.
– tchrist
Sep 22, 2017 at 0:19
• Would rather, want, and similar verbs presuppose unreal (irrealis) states in their complements. You can't want something you already have, after all. With the plane leaving, either an infinitive (not present; tenseless) or a past tense left early in the morning would be fine, with no difference. In both cases, the plane is not scheduled to leave early in the morning. In Debby's case, either spend (an infinitive) or past tense spent are grammatical, and in both cases the boyfriend is not (and has not been) spending Friday nights with her. "Subjunctive" is a useless category. Sep 22, 2017 at 3:30
• @John Lawler But you can desire/want a continuation / realisation of or a change to the status quo / planned schedule. Sep 22, 2017 at 15:29
• My book has a section where I must change the verb to be in the subjunctive form or the contrary to fact form. For example, a question asks "John's sister would rather that he _____ (negative of embarrass) her in front of her friends all the time". There is only one answer that correctly fills the blank: not embarrass (which comes from present subjunctive form). If I thought this sentence was contrary to fact, I would have filled in didn't embarrass, but this would be wrong. In other words, how can I know what is contrary to fact and what is subjunctive without looking at the verb? Sep 22, 2017 at 19:43