One of my followers on Twitter named Aaron Allbrooks tweeted, “Why does ‘let’s know when you arrive’ sound weird, but ‘let us know when you arrive' doesn’t?” It was a good question. I tweeted back at him, “And conversely, ‘Let us go to the mall’ sounds weird, but ‘Let’s go to the mall’ sounds fine.” Also, just imagine a group of prisoners begging their captor to set them free. Let us go makes sense; Let’s go doesn’t. What’s going on with let us and let’s? Let’s find out.
Traditional English-grammar doesn’t distinguish sentences like Let’s go and Let us know. It classifies them both as imperatives. The understood subject of each is You, and us is the direct object of let. But as Aaron noticed, the two kinds of sentences don’t behave the same way. Sometimes you can contract let us to let’s, and sometimes you can’t. In fact, as reported in the Cambridge Grammar of the English Language, this is only one of five differences between sentences beginning with let’s and let us.
At this point, we need to have a name to refer to the two kinds of let-sentences. The Cambridge Grammar of the English Language, or CGEL for short, refers to sentences like Let us know as “ordinary imperatives,” and to sentences like Let’s go as “first-person inclusive let-imperatives.” By first-person inclusive, the authors mean that if I say Let’s go, I’m not talking about me and some other people; I’m talking about me and you. They also use the term “open let-imperatives” to refer to very similar sentences that don’t involve us. These are sentences such as Let x be a rational number between zero and infinity, Let that be a lesson to you, or What God has joined together, let no one put asunder, or even sentences with dummy subjects, such as Let it snow and Let there be light. I’ll use the term special let-imperatives to refer to both kinds: first-person inclusive let-imperatives and open let-imperatives. Not only is this term more convenient, but also most of the differences we’re going to talk about apply to both kinds of special let-imperatives.
Ordinary or Special?
Now, on to the differences between ordinary imperatives and special let-imperatives. The first one that CGEL lists is about the contraction of us, which is what Aaron was noticing. CGEL points out that us cannot be contracted in ordinary imperatives, which is exactly what Aaron tried to do when he wrote, “Let’s know when you arrive.” CGEL states further that you can’t contract us in declarative or interrogative sentences, either. You wouldn’t say They didn’t want to let’s join in instead of They didn’t want to let us join in. And you wouldn’t say Will you make’s breakfast? instead of Will you make us breakfast? (Actually, this is an inadvisable question anyway, because the person you’re asking might answer, “Abracadabra! You’re breakfast!”)
Not only can you contract let us if you’re uttering a special let-imperative; usually, you will. The most common place to hear an uncontracted let us is in a religious context, probably in the sentences Let us pray or Let us rejoice. For example, when I checked the Corpus of Contemporary American English, the top two words most associated with uncontracted Let us are rejoice and pray. I also found that with negative suggestions, let us not is more common than you’d expect, although it’s still in the minority compared with let’s not. Interestingly, let us not is especially common with the verb forget. In fact, that one verb flips the usual pattern, so that let us not forget is actually almost three times as common as let’s not forget. If any of you have guesses as to why that’s so, please leave a comment.
The second difference between ordinary imperatives and special let-imperatives has to do with whether you can have an explicit subject. For an ordinary imperative, the subject can be understood, as in the command Be quiet; or it can be explicit, as in No, you be quiet, or All right, everyone be quiet! However, take the sentence Let’s go, and put a you in front of it—You let’s go—and it doesn’t make sense anymore. And I’m laughing as I imagine the classic holiday tune: “Let it snow, no you let it snow, no YOU let it snow!”
The third difference has to do with interrogative tags. These are sequences of a contracted auxiliary verb and a pronoun that you can put at the end of a sentence, such as isn’t it, doesn’t she, or am I, to turn it into a question. Usually, these come at the end of a declarative sentence, as in It’s hot, isn’t it?, but you can use the tags will you, won’t you, and would you after an ordinary imperative. For example, you could say Give me a hand, would you? or Keep it down, will you? This doesn’t work with first-person inclusive let-imperatives. Let’s go, will you? doesn’t make any more sense than You let’s go. On the other hand, you can say Let’s go, shall we?, which shouldn’t be possible at all if the subject of Let’s go is truly an understood you.
The fourth difference has to do with negation. If you want to suggest not doing something, there are at least two ways to do it with a first-person inclusive let-imperative. The most common way to negate Let’s go is Let’s not go, but another way is Don’t let’s go. They both mean the same thing. With an ordinary imperative, though, the way you negate it affects the meaning. For example, let’s consider an ordinary imperative sentence about a party. If your teenage kids say to you, Let us go to the party, it’s a probably a party that their friends are having, and they’re requesting permission to go. On the other hand, if they say Let us not go to the party, it’s probably a party your friends are having, and your kids are asking permission to stay home. And if they say Don’t let us go the party, it’s probably once again a party that their friends are having, but this time they don’t want to go, and they want you to give them a socially acceptable reason to avoid it: “Sorry, my boring, overprotective parents won’t let me.” That’s a pretty big difference in meaning.
The final difference for first-person let imperatives involves ellipsis—not the punctuation mark, but grammatical ellipsis. Ellipsis is the use of just a fragment of a sentence when the rest of it is clear from context. With an ordinary imperative, like Aaron’s Let us know when you arrive, someone else can second the request, and say, Yes, please do instead of saying the full sentence Yes, please do let us know when you arrive. Alternatively, they could negate the request by saying, No, please don’t. In contrast, with our Let’s go example, you can second the suggestion by saying Yes, let’s, or reject it by saying No, let’s not, but you can’t say, Yes, please do, or No, please don’t.
A Special Marker
All these differences between ordinary imperatives and first-person inclusive let-imperatives show just how much it has become specialized. Rodney Huddleston and Geoff Pullum, the authors of CGEL, even argue that it’s so specialized now that it shouldn’t even be analyzed as an imperative anymore. They argue that we should think of let’s as a special marker that introduces a first-person imperative. One piece of evidence they cite has to do with first-person inclusive let-imperatives that put in an explicit subject between the let’s and the verb, as in Let’s you and me go to the mall. Some speakers would say it this way: Let’s you and I go to the mall. The subjective pronoun I, the linguists argue, shows that these speakers don’t think of the noun phrase you and I as the object of let anymore, and are treating it as the subject of go. I don’t find this argument convincing, because it’s also well-known that many speakers routinely use I instead of me when they coordinate it with another pronoun, because they consider it to be more formal or polite. Just think of all the confusion over the phrase between you and me, which is the standard version, and between you and I.
Thanks to Aaron for pointing to an interesting topic. I don’t know about the rest of you, but talking about this is making me hungry, maybe for a nice bacon-let’s-and-tomato sandwich!
This article was written by Neal Whitman, who has a PhD in linguistics and blogs at literalminded.wordpress.com.
Let's go image courtesy of Shutterstock