Here a sentence from my grammar book.

"It is as difficult to swim as drive.

I know when 'than' is used in a sentence, then it takes bare infinitive. Like..

"She is better able to speak than(bare infinitive) write."

Does it apply on my first sentence also ?

  • 3
    I'd say that both bare and to-infinitivals are possible.
    – BillJ
    Mar 31 at 14:41
  • 2
    Grammatically, you can pretty much omit as much or as little as you like after "as". Likewise with "She is better able to speak than she is able to write". You seem confused about how to use "than" in this sort of comparison; I think there are pre-existing questions somewhere.
    – Stuart F
    Mar 31 at 14:51
  • The point is that the prepositions "as" and "than" can take either bare or to-infinitival comparative clauses.
    – BillJ
    Mar 31 at 15:03
  • It is as difficult to swim as [to] drive. Alternatively, Swimming is as difficult as driving. Mar 31 at 16:06

2 Answers 2


This construction has nothing to do with the equative marker as or the comparative marker than. They appear in equative and comparative constructions, where they have their own jobs. They don't control the verbs or verb forms that are used with them, so, to answer the question the way it was asked, as doesn't take anything.

The reason for the bare infinitive is that the to is not required, since the main predicate governs an infinitive in both clauses, and to was used in the first clause, so it's redundant (but possible) in the second. It's a form of conjunction reduction, though it functions inside a construction.

In the two example sentences in the question

  1. It is as difficult to swim as (to) drive.
  2. She is better able to speak than (to) write.

the repeated infinitive marker to is deleted in the parallel infinitive clauses at the end, but it could have been left in. The omission is optional, not obligatory, and its optionality is part of the equative and comparative constructions. These constructions have any number of optional attachments, like a Cuisinart:

  • It is as difficult for her to drive carefully as it is for him to drive carelessly.
  • Her driving is as difficult for me to observe as it must be for her husband to experience.
  • Driving with her is as delightful as flying.

In any of the above, substitute more ... than for as ... as to get a comparative instead of an equative construction. Superlative, the highest in that syntactic paradigm, works differently from the first two, because its baseline clause doesn't have to be parallel:

  • Driving with her is the best <insert description>.

Oh, and grammar is spelled without E's. It's pronounced the same as grammer, which makes more sense, but the spelling's wrong. Normally spelling isn't noticed much, but grammar is a word you really want to spell right.

  • 1
    I think it's preferable to say that what you call an 'equative' construction is also a comparative construction expressing scalar comparison of equality. X is as heavy as Y involves comparison just as much as X is heavier than Y and syntactically they are alike in that the Y element can be realised by a comparative clause.
    – BillJ
    Mar 31 at 16:42
  • "Equative", "comparative", and "superlative" are the traditional names for the syntactic constructions, and that's good enough for me. What they express is syntactically irrelevant. Mar 31 at 17:36
  • 1
    Of course it's important, as I explained in my comment. Perhaps you should take account of more modern (and more accurate) analyses.
    – BillJ
    Mar 31 at 17:49
  • 1
    If you say so; I'm sure I wouldn't be able to perceive their inherent modernity and accuracy without your pointing it out. Mar 31 at 17:51

This is an example of parallelism. The full statement is "It is as difficult to swim as it is difficult to drive." "As" is functioning as a conjunction, bringing together two phrases. In both phrases, the verb is acting as the subject of the copula, with "difficult" as the subject complement (there is the dummy pronoun "it" that is, strictly speaking, directly being the subject, but the sentence is effectively "To swim is as difficult as to drive is difficult"), so the infinitive is used as it functions as a noun. The duplicated parts are not repeated, giving just "It is difficult to swim as drive". The word "to" can be included in both parts, but including "difficult" twice comes off as odd.

In your other example, the full sentence is "She is able to speak better than she is able write", with "better than" acting as a conjunction, but "better" is allowed to be moved to right after the verb, and the repeated "she is able" and "better" dropped.

Some more examples of parallelism would be "She worked longer on her Math homework than [how long she worked on her] English [homework]" and "She had found and [she had] eaten the candy" with the parts in brackets being droppable. While "She eaten the candy" is not grammatical, the parallelism allows the repeated "had" to be implied. In the same way, the "to" in your sentence is implied.

  • Actually, "as" is a preposition with the comparative clause "drive" as its complement. Comparative clauses are obligatorily reduced relative to the structure of main clauses. Here, the clause is reduced to just the predicator "drive". In the other example, "than" is also a preposition with the comparative clause "write" as complement. "Better" is an adverb modifying "able".
    – BillJ
    Apr 1 at 8:50

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