When a to-infinitive is used with words like "too" and "enough" what word does it modify? For example

The animal moves too quickly to be captured.

The bag is too heavy to lift.

He is scared enough to fire his gun.

At first I thought the to-infinitive modified the adjectives and adverbs quickly, heavy, and scared, but I got confused on later example sentences.

Bob is too eager to fight.

Bob is too eager to fight to wait.

It seems strange for two to-infinitives to modify an adjective at the same time, when it occurred to me that the to-infinitive may be modifying "too" instead. Is this true? In any case, "to wait" does not seem to modify the same way "to fight" does in the latter sentence, but I haven't found a good explanation on how a to-infinitive like "to wait" works with words like "too" and "enough" in dictionaries. Also, the first three sentences don't make much sense without "too" or "enough". "The animal moves quickly to be captured" has a much different meaning than "the animal moves too quickly to be captured."

  • I love this question (and the ambiguities in the samples). 'Too' is modifying a hidden determiner 'much' which applies to the adjective, and the adjective has an object, which is an infinitive.; and that adjective phrase can inhibit another infinitive. Wow!
    – AmI
    Commented Feb 3, 2016 at 20:44
  • 1
    Bob is too eager to fight to wait to see what happens. There's nothing wrong with "stacking" infinitives as with the last two there, and it's just irrelevant that OP happens to have preceded his example with a homophone and a syntactically distinct instance of to. Commented Feb 3, 2016 at 21:10
  • @FumbleFingers They aren't being stacked in any meaningful sense at all. The too is modifying an adjective phrase with to-infinitive in, but the other to is part of a clause which is an Indirect Complement of the adjective i.e. it's licenced by *too. The first to-infinitival doesn't rely on the existence of the adverb too at all - unlike the second. In your example, the first infinitival is a Complement of the adjective, the second is a dependent of too and therefore an Indirect Complement of the adjective eager. The last is an adjunct of purpose within the wait infinitival. Commented Feb 3, 2016 at 21:36
  • 1
    @FumbleFingers ... So there's no "stacking" in any syntactic sense of the word. Each to-infinitival there is completely different in terms of grammatical relations, dependencies, meaning and so forth. You can't stack infinitivals like that. Although you can catenate them: "I want to try to want to learn to play to win", for example. But that's ten thousand miles away from OP's examples and your own. Commented Feb 3, 2016 at 21:39
  • @Araucaria: My comment was intended to explicitly point out that although OP's example is really nothing more than "chance collocation" (plus a totally irrelevant homophone), even if the infinitives were being "stacked", there wouldn't be anything wrong. Commented Feb 3, 2016 at 21:41

7 Answers 7


As pointed out in this answer,

Too is a Negative -- too Adj to VP means 'so Adj that Not VP'

A bag that is too heavy (for anyone) to lift means a bag that can't be lifted (by anyone).

As for what modifies what, the infinitive is the [to VP] part of the [too Adj [to VP]] construction. That infinitive doesn't modify any single word; rather, it says there is Adj enough to negate VP.

  • I would call 'enough', 'so', and 'too' (in these cases) 'intensifiers'. 'Enough [some]' has also evolved to where it could be called a 'determiner'. Because 'enough' and 'so' do not inhibit action, they can appear with 'that' instead of just (hypothetical) 'to'.
    – AmI
    Commented Feb 9, 2016 at 18:50
  • useful but incomplete answer! It does not explain what each of the two consecutive full infinitives modify.
    – user58319
    Commented Feb 15, 2016 at 17:11
  • @583 'A is [too Adj to V₁] [to V₂].' There are few possibilities for the choive of adjective, and V₁. 'He was too happy to see them to remember to give them the book.' 'She was too keen to see Ben to wait at the hotel.' ' He was too unwilling to forgive Bob to speak to him.' 'The problem was too difficult to solve to include in a GCSE exam,' Commented Mar 16, 2022 at 15:03

"too" modifies "quickly" "too quickly" modifies "to be captured"

"enough" modifies "scared" "scared enough" modifies "to fire his gun."


In your first three examples:

The animal moves too quickly to be captured.

The bag is too heavy to lift.

He is scared enough to fire his gun.

Too modifies quickly which is also modified by to be captured. In the second, too and to lift modifies heavy. Finally, scared is modified by both enough and to fire his gun.

Bob is too eager to fight.

Bob is too eager to fight to wait.

The first one follows the same rule as the last three: too and to fight modify eager. However, your last example is an odd instance of an infinitive following another. It would be best to visualize the phrase:

too eager to fight


too x to y

where x=eager and y=fight in your second to last example, but in your last, it is x=eager to fight and y=wait. The only difference to the others is that to wait and too have the company of to fight in their modification of eager.


I just think that if you use a verb after an adverb/or adjective you need a "to-infinitive", called "infinitive of purpose". This is regardless the use of "too" or "enough".

For example:

It is difficult to lose weight.

The box is too big to carry.

They didn't fly high enough to reach the sun.

I hope this helps.


This may be considered a layman's explanation, in comparison to John Lawler's — mine is the familiar made-easy-type.

Too: an adverb, meaning more than / less than sufficient or necessary. It qualifies adjective/ modifies adverbs being placed before them and when followed by infinitive in a sentence, the 'excess' in its meaning assumes a negative connotation. Compare:

The mango is very sweet.(i.e, you like it)

The mango is too sweet.(i.e, you dislike it)

Enough: an adverb used to mean just sufficient and whether there is an infinitive or not it does not not hold such nicities as 'too'. However, when 'enough' makes an adjective or adverb stronger or weaker, it is placed after them as opposed to 'too'

'Infinitive' is a nonfinite verb which does not have subject, tense, mood or number but can be modified by adverb. In the examples of the post the adverbs are modifying adjectives/ other adverbs and the infinitives in an indirect manner. To my mind in sentences as such with 'too (adj/adv) and infinitive following has a kind of correlation not to be substituted by gerund— a syntax unique to infinitive.

There may occur as many nos. of infinitives as the sentence requires but they never qualify or modify but are rather qualified or modified by adjectives or adverbs in a manner as stated above.

The animal moves too(adv) quickly (adv) to be captured. = The animal moves so quickly that it cannot be capturd

  • The bag is so heavy (adj) that it cannot be lifted.

**He was scared to such an extent that he had to fire his gun.(a compulsion, no negation)

• Bob is so eager that he would not fight

••Bob is so eager that he cannot wait for a fight.

With use of two infinitives a sense of affirmation has been brought in : Bob likes to fight here and now.


As John Lawler says in his answer,

The bag is too heavy to lift.

means the same as

The bag is so heavy that it cannot be lifted (by anyone).


It is such a heavy bag that it cannot be lifted (by anyone).

It is a special type of result clause: the quality of 'heaviness' attached to the bag has to reach a certain degree, a certain intensity, for the result to exist; weight only becomes the cause of the impossibility to lift the bag beyond a threshold value. The subordinate clause combines comparison and cause and effect relationship. The bag is only just heavier than the weight that would make someone able to lift it.

The sentence

Bob is too eager to fight to wait.

can be rephrased as

Bob is so eager to fight that he cannot wait.

The adjective 'eager' is modified/completed by the infinitive 'to fight'. Now 'eager to fight' is an adjective phrase that could be replaced with a single-word adjective like 'quarrelsome', and it is this whole adjective phrase which is modified by 'to wait'. The two infinitives do not modify the same adjective exactly!


The question what does the to-infinitive modify leads to nowhere. I think sentences with too + adj + tif (adj = adjective, tif= to-infinitive) can be reduced to two sentences.

  • The bag is too heavy to lift - The bag is very heavy. Impossible to lift it.

With "too heavy + tif" we have a possibility to melt the two sentences together.

The view of Acharya above is in the same line. His view: The bag is so heavy that it can't be lifted.

So the tif corresponds to a second sentence or to a subclause of consequence. The only thing we can say is the second sentence or the subclause refer to the first part with "too + adj" and indicate the consequence.

  • downvoted because 2 separate sentences do not show the connection: heavy [beyond a limit] [such that] to lift [is not do-able]
    – AmI
    Commented Feb 9, 2016 at 18:36
  • However, in our school days we were actually asked to make such '... too...to' construction complex just in the line of rogermue. Commented Feb 10, 2016 at 14:53

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