As if/as Though+present. and As vs if

Question

my Grammar book saying: The verb after AS IF/as though is always in the past subjunctive,no matter what tense the sentence is and If the verb BE directly follows AS IF/as though,we use "were" for all personal pronouns.

But see these sentences ↓:

1. Since they cannot see him with their literal eyes, they act as if he is not seeing them. (bible)

2. Among fellow Christians, we should never feel threatened, as if others are trying to outdo us or take our place.(Bible)

3. you talk as though we’re never going to see each other again.

and Can I use "as" instead of "as though/as if" in these sentence.

and which is correct?

4. Work Hard as you are born for struggle or work hard like you are born for struggle

5. He is Hard working as he born for Struggle or he is hard working like he born for struggle.

6. he is smiling like he know everything or He is smiling as he know everything.

7. Slap him powerfully as you are killing him by the slap or slap him powerfully like you are killing him by the slap

he is doing like a teacher(it means he isn't a teacher) he is doing as a teachee (he is teacher)

but 8. he is doing as he is a teacher or he is doing like he is a teacher?

Answer 1

I have a bunch of info below to walk you through the ideas here, but in general, your substitutions of as/like all change the meaning of the sentences.

The construct "A as B" is the same as "A because B" or "B therefore A". You are stating a cause and effect relationship.

"A like B" or "A as if B" is a creating a speculative relationship. It implies: "Even though "A" is not a "B", "A" is doing something in a "B" like manner.

Back to your samples - I'll start with your 7th as this one powerfully illustrates the point.

Your first clause can be rewritten:

Slap him powerfully "because" you are killing him via the slap.

or

You are killing him with this slap therefore (you must) slap powerfully.

versus

Slap him powerfully, in a manner similiar to if you were attempting to kill him via the slap (though you are probably not trying to kill him...)

You can see this conveys quite a different meaning. The first is attempted murder. The second is a a slap that could possibly be murder-like, but is instead more a practice strength blow.

Sentence 4 and 5 - the first clause, substitute "because" and the meaning is identical. The second clause, speculative and assumes that you are not "born of struggle" but must act like you are.

Again, the same pattern hold for 1,2,3. Substituting just "as" is not correct and in some cases, is not grammatical.

Sentence 6 and 8 - same. 8 especially implies you are "not a teacher, but acting like you were one." This reminds me of an English TV commercial trope - "I am not a pilot, but I stayed at a Holiday Inn Express last night..."

The difference in grammar is indeed subtle, but you can see that it implies quite a bit.