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I know from verious other discussions that 'can not' and 'cannot' are basically both correct but 'cannot' is being used more often. Nonetheless what happens if I have a 'not only...but also' construction like in the following sentence:

"Heat pumps cannot only be used for space heating but also for space cooling."

Is it also correct to use 'cannot' in this context? I'd appreciate every comment.

PeterBe
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    I'd prefer to say not only can heat pumps be used for space heating, but also for space cooling. – Decapitated Soul Apr 18 '20 at 15:50
  • Why not use "either,,,,,, or" – Centaurus Apr 18 '20 at 15:53
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    'Not only... but also...' structure is inversion. If you want to invert your sentence, you need to split up 'cannot' and put 'not' at the beginning. – Decapitated Soul Apr 18 '20 at 16:00
  • As written, it is a denial that heat pumps can only be used for space heating. It communicates differently from the “can [not only ... but also]” variant. – Lawrence Apr 18 '20 at 16:02
  • Both cannot* and can not are acceptable spellings, but the first is much more usual. You would use can not when the ‘not’ forms part of another construction such as ‘not only.’* – FumbleFingers Apr 18 '20 at 16:06
  • Thanks for all the comments (@FumbleFingers: No this does not answer my question). I am still unsure about what to do. Can I just use the same sentence and split up cannot: "Heat pumps can not only be used for space heating but also for space cooling." – PeterBe Apr 18 '20 at 16:09
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    I thought I included all the relevant text in my actual comment, so you shouldn't have even needed to follow the link. Yes - you should split *cannot* in your context, because *not* forms part of the collocation *not only* (itself part of the standard *not only X but also Y* construction), rather than negating the verb *can*. – FumbleFingers Apr 18 '20 at 18:18

1 Answers1

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You have two problems here. Let's start with correlative conjunctions and parallelism . . .

Correlative conjunctions—either/or, neither/nor, not only/but [also]—come in pairs. What follows each part of the pair must be parallel: both nouns, both verbs (same tense), both prepositional phrases, both independent clauses. In the case of your sentence, it should read:

Heat pumps can be used not only for space heating but also for space cooling.

or

Heat pumps can be used for not only space heating but also space cooling.

Now you have parallel prepositional phrases or parallel noun phrases. And, voila, the use of cannot is impossible.

But even if we used parallel verbs, cannot would still be incorrect:

*Heat pumps cannot only be used for space heating but also be used for space cooling. (incorrect)

You need to use can not. Why? Simply because not belongs to the correlative conjunction pair not only/but also—not to can:

Heat pumps can not only be used for space heating but also be used for space cooling.

Tinfoil Hat
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  • Thanks Tinfoil Hat for your answers. Is the last sentence your final adivce:"Heat pumps can not only be used for space heating but also be used for space cooling." – PeterBe Apr 18 '20 at 17:22
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    The first or second would be my preference. The first sounds a little better to me, even though using for twice makes it wordier. – Tinfoil Hat Apr 18 '20 at 17:50
  • Thanks for the answer Tinfoil. Can I basically also use the constrction:"can not only... but also" instead of "not only can ... but also". For me this sound better? – PeterBe Apr 18 '20 at 20:06
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    @PeterBe: You can do that, but the sooner you introduce not only, the more you have to repeat in order to maintain the parallel structure: Heat pumps not only can be used for space heating* but also can be used for space cooling.* Also, if you do want to branch at the verb, it is more natural to do it after the auxiliary (in this case, can), which would be the last example in my answer. Again, the most natural is the first sentence. – Tinfoil Hat Apr 19 '20 at 00:58
  • Thanks Tinfoil Hat for your answer. What about the following sentence with different verbs. Is it correct "Meters that can not only monitor the electricity generation and demand and at high temporal resolution but also communicate with other components in the grid are currently being rolled out" – PeterBe Apr 19 '20 at 06:57
  • @PeterBe: Your verb parallelism is correct. Stylistically, your relative clause is so long that the reader gets lost between the meters and roll out. Try, perhaps: Meters currently being rolled out can not only monitor electricity generation and demand at high temporal resolution but also communicate with other components in the grid. – Tinfoil Hat Apr 19 '20 at 14:55
  • Thanks Tinfoil Hat for your answer. The problem with your suggested sentence "Meters currently being rolled out can not only monitor electricity generation and demand at high temporal resolution but also communicate with other components in the grid." is that a reader could think that all meters that are currently rolled out have these advanced features. This is not the case. Only a small share of meters that are currently being rolled out have these features – PeterBe Apr 19 '20 at 15:23
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    Ah, then this is the perfect case for the dummy there: There are meters currently being rolled out that can not only monitor electricity generation and demand at high temporal resolution but also communicate with other components in the grid. – Tinfoil Hat Apr 19 '20 at 15:27
  • Thanks Tinfoil Hat for your answer. What about this sentence:"Heat pumps that not only can be switched on and off but regulate their power consumption by changing the compressor speed are especially beneficial for smart grids"? Is this correct? – PeterBe Apr 19 '20 at 17:13
  • Similar problem—too much stuff between the beginning and the end. Try an inversion: Especially beneficial for smart grids are heat pumps that can not only can be switched on and off but also regulate their power consumption by changing the compressor speed. – Tinfoil Hat Apr 19 '20 at 21:02
  • Thanks Tinfoil Hat for your answer. Why are you using two times can in this sentence " ...that can not only can be switched..." I do not understand this and for me this sound weird. Which of those 4 types mentioned in your answer are you talking about? – PeterBe Apr 20 '20 at 09:59
  • And maybe the last example because I think this has not been covered so far. What about this sentence: "Changing the electrical load not only leads to better integration of renewables. It can also stabilize the grid and improve the efficiency" – PeterBe Apr 20 '20 at 10:07
  • Would you mind answering my last question/examples (there won't be any further example). I'd really appreciate it – PeterBe Apr 20 '20 at 18:29
  • Changing the electrical load not only leads to better integration of renewables but can also stabilize the grid and improve the efficiency. or Not only does changing the electrical load lead to better integration of renewables, it can also stabilize the grid and improve the efficiency. – Tinfoil Hat Apr 21 '20 at 23:23