The standard model, however, failed to explain gravity. Enter string theory to rectify the problem. (From an ACT test)

As the bold sentence above, it throws me off when I see a verb lead a sentence: where is the subject?


3 Answers 3


The word "Enter" is used in scripts and screenplays - the kind that actors read from - as a stage direction. For example, "Enter Hamlet" means that the character Hamlet enters the stage at that point in the script. A stage direction might also add other detail, for example "enter Hamlet holding a sword".

It is a fairly common idiom to mimic this kind of stage direction in other kinds of speech or writing as a way of saying that something entered the story or timeline at that particular point.

In your example, 'string theory' is the subject. It means that up until the point that string theory was posited, the standard model of physics had failed to explain gravity.

  • 5
    The Oxford English Dictionary mentions that "enter" as a stage direction is usual even when the subject is singular (as in this case) because the form "was apparently originally subjunctive", though later sometimes interpreted as an imperative.
    – rjpond
    Commented Oct 8, 2020 at 10:38
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    To me it gives the whole scene a dramatic effect. I almost expect to read next - Drum roll, fanfare of trumpets.
    – mdewey
    Commented Oct 8, 2020 at 13:10
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    Possibly worth noting that this is a now-unusual use of the imperative, which typically takes an implied "you" but didn't always. Commented Oct 8, 2020 at 17:39
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    @mdewey Indeed, this use anthropomorphizes string theory as a character who suddenly joins the action.
    – Barmar
    Commented Oct 8, 2020 at 20:32
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    Exit, pursued by a bear. Commented Oct 8, 2020 at 22:16

The word "enter" is being used for dramatic effect (as @Astralbee explains), in a reference to stage direction. However, this usage of "enter" is in the imperative mood. The subject of imperative verbs is second person (i.e. "you"), but it is not said (in linguistics terminology, it doesn't have a surface form).

In English, the syntactic subject of the verb is probably best understood as the noun that has nominative case. Case is mostly marked on pronouns in English, such as "I" (subject) versus "me" (object), "he" versus "him". In this context, *"Enter he to rectify the problem" is clearly ungrammatical (to me, a native speaker of English), while "Enter him to rectify the problem" is fine. So, I would suggest "string theory" is the object of "enter", not the subject.

As suggested, this is a grammatical flourish referencing stage direction. In stage direction notes, the person who is being directed to do something is the director. So, a sentence like "enter Hamlet stage right" this could be rephrased as "You, director, enter Hamlet stage right".

Lastly, "enter" has (at least) two different meanings where what happens to the object differs. "Casey entered the building" means that Casey moved themself into the building. I think this is the meaning that is commonly associated with these stage directions because there is only one noun and it is a moving thing, so it is interpreted as the subject of the sentence. But there is also "Casey entered their card", where Casey is moving the object, not themself.

To put it all together, both "enter Hamlet stage right" and "enter string theory to rectify the problem" use the second meaning, where the director, or some metaphorical director (the arc of history, God, etc.), is entering Hamlet into the play or string theory into the world as one enters an item into a receiver.

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    That's all highly speculative. The OED regards "enter" as in origin a subjunctive, with "string theory" (in this case) as the subject. "Exit" is used when someone exits the stage, but the sentence "you, director, exit Hamlet" would be ungrammatical. Also, I remember seeing in old plays "exeunt" (Lat.: they exit) used when multiple people were leaving the stage at once. (The original usage was the subjunctive "exeant", but at some stage "exeunt" took over. But my point here is that "exeunt" could in no way be an imperative.)
    – rjpond
    Commented Oct 8, 2020 at 21:51
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    @rjpond what did I write that was speculative? Everything that I wrote was based on standard methods in linguistics. The OED has history of words, but that doesn't speak to any usage of what how a native speaker actually uses or doesn't use a word in a language. It seems like we're on opposite sides of the divide between literature and linguistics, so I don't want to stoke that argument, but I think you arguing that a child who can understand "enter the hero to save the day" has any inkling of old Latin texts is much more speculative than comparing constructions.
    – dantiston
    Commented Oct 8, 2020 at 23:57
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    Imperative is a mood, not a voice. Commented Oct 9, 2020 at 0:09
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    @rjpond regarding "exit", "exit" and "enter" are different words, so it's entirely probable that they have different behaviors. *"Casey exited their card" is ungrammatical, as well, so I would expect "the director exited Hamlet" to be ungrammatical. I think there's lots of things going on with "exit", but I will leave that as an exercise for another time.
    – dantiston
    Commented Oct 9, 2020 at 0:13
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    I can believe that synchronically most native speakers might regard the stage direction "enter" as an imperative (though even here I don't see that we have clear evidence). But you go well beyond that in asserting that the imperative is addressed to the director. I just don't see it. I would also prefer "Enter he who will rectify the problem" rather than "...him...".
    – rjpond
    Commented Oct 9, 2020 at 7:34

You, the reader, are the subject of the sentence. String theory is presented for your consideration, as it were, a theatrical character entering onto a stage.

The subject is implicit, but filling in the gaps, the sentence reads:

[You, observe] string theory enter [the scene] to rectify the problem.

The sentence is phrased imperatively, immediately, and in the present tense. It has the effect of calling the reader's attention momentarily to "new action on the scene".

Primarily, you (as subject) observe/consider (verb) string theory (the object). This is the fundamental structure of the sentence, as written:

[You, observe] string theory

Secondarily, string theory (as subject) enters (verb). As written, this is structured as an infinitive phrase, where "[to] enter" is the infinitive:

...string theory [to] enter [the scene]

  • The metaphorical theatrical director is not the subject of the sentence because string theory is being passively presented for consideration. No one is actively directing it onto the stage.
    – Gooseberry
    Commented Oct 9, 2020 at 8:58
  • Please provide reasons for downvotes. If you disagree with my answer, I'd be happy to discuss!
    – Gooseberry
    Commented Oct 9, 2020 at 17:57

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