cleft and pseudo cleft sentences(All (that) I did was **touch** the window, and it broke.)

Question

Why is the following example (A) correct as a cleft sentence, but not sentence (B)?

As I have learned, we can only use 'pronoun, noun, gerund, or infinitive', not the base form of verb (help) after noun clause. I get confused.

A "All (that) I did was touch the window, and it broke."

B "What makes me feel happy is help the poor."

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Are these following sentences correct grammatically and logically?

All (that) I did was (to) touch the window, and it broke.

All (that) I did was touch the window, and it broke.

All (that) I did was touching the window, and it broke.

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What makes me feel happy is to help the poor.

What makes me feel happy is helping the poor.

What makes me feel happy is help the poor.

Answer 1

Because the bare infinitive help is not understood to be a nominal (which goes with what I like) but an action. What I want to do is help the poor. What makes me happy is to help|helping the poor.

I like look out the window. ^{ungrammatical}

I like looking out the window. ^grammatical

I like to look out the window. ^grammatical

Cleft:

What I like is look out the window.^{ungrammatical}

What I like is looking out the window. ^grammatical

What I like is to look out the window. ^grammatical

Normal: I touched the window.
Cleft: What I did was touch the window.

The predicate complement of the cleft must supply either a nominal or an action according to the needs of the verb in the cleft.

Here, that verb is did, and it is looking for an action. When did has the meaning "performed an action" it wants an action complement. The bare infinitive is an action:

I did shop. ^grammatical
I did eat. ^grammatical
I did play. ^grammatical
I did sky. ^{ungrammatical}

Thus:

What I did was touch the window. ^grammatical

What I did was to touch the window. ^{ungrammatical [some might say marginal]}

What I did was touching the window. ^{ungrammatical}

Answer 2

Cleft sentences and Wh-Cleft sentences have different forms and different rules. They don't work the same way, even though they're often used for the same purposes -- to point out the important part of a sentence.

There are several different kinds of cleft sentences, but all of them isolate some aspect of the sentence in a special construction, on one side of a special word that's inserted by the clefting rule to separate the important part from the identification part. It's called the fulcrum of cleavage (boldfaced below):

• I ordered a chocolate malt ==> It was a chocolate malt that I ordered.
  An It-Cleft

It-Cleft sentences have a dummy it is/was followed by the extracted item with a restrictive relative clause identifying it. The relative pronoun (that in the example above) is the fulcrum of cleavage. Note that these sentences are not reversible, like Wh-Clefts.

• I ordered a chocolate malt ==> What I ordered was a chocolate malt.
  A Wh-Cleft

Wh-cleft sentences have an embedded question subordinate clause on one side of a form of auxiliary be that acts as a fulcrum (was in the example above). Since the fulcrum forms an equational sentence, Wh-cleft sentences are reversible in most cases:

• I ordered a chocolate malt ==> A chocolate malt was what I ordered .
  Another Wh-Cleft

As far as the complements are concerned, clefts like What/All I did was ... should be followed by an infinitive clause what/all I did was (to) touch it, with or without to, because do takes an infinitive complement. But clefts like What I like is ... can be followed by a gerund clause what I like is touching it because like can take a gerund complement. Like can also take an infinitive (I like reading/to read), so what I like is to touch it is also OK.

Basically, the kind of complement clause is governed by the verb, not by what construction the verb occurs in. Verbs determine almost everything.