It is important

  • lingobingo

    Senior Member
    English - England
    In “It is important to understand this…”, the it is a dummy subject. It has no intrinsic meaning but is used to facilitate that grammatical construction — rather than expressing the same thing in the way grassy explains.
     

    SevenDays

    Senior Member
    Spanish
    It is important to understand this, because when a bare infinitive is used to form a tense, it is not affected by time or subject-verb agreement.
    What is a bare infinitive? - English Lessons in Brighton
    I know the "it" in "it is not affected..." refers to "bare infinitive" and thus acting as a pronoun but please explain the use of "it" in "it is important..."
    I'm not sure what they mean by "when a bare infinitive is used to form a tense," because infinitives don't have "tense." Tense is always expressed by another verb (the "main verb"). Infinitives are non-finite verbs, and they always agree with subjects in pronoun form (me, him, them, etc.), but it so happens that infinitives can appear without explicit subjects (and often do), because mentioning the subject is not important.

    In your example, there's a transformation process that makes the use of "it" obligatory. Often, for pragmatic reasons, English doesn't like infinitives appearing first in a sentence. And so there's nothing syntactically wrong with To understand this is important, but the message is somewhat diluted; "important" sort of gets lost there at the end. To make the sentence more expressive, we place the infinitive at the end, leaving "important" closer to the front; this is known as "extraposition:" is important to understand this. Of course, this is not a grammatical sentence. Putting the auxiliary verb "is" (a finite verb) first means that we need to give "is" a subject, because all finite verbs go with subjects. And this function (subject of "is") is performed by "it" (a "dummy subject," as already mentioned.) Now, we have a grammatical sentence.

    It is important to understand this

    as I said above, infinitives often appear without explicit subjects. If you need to mention the subject of the infinitive, sometimes syntax requires the use of "for," a word (known as "complementizer") which introduces the pronoun functioning as subject of the infinitive:

    It is important for us to understand this ~ It is important for me to understand this
     
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