The Grammaring Guide to English Grammar with Exercises

AS IF / AS THOUGH

Clauses that start with as if / as though describe an unreal or improbable situation if they are followed by an unreal tense (the past subjunctive or the past perfect subjunctive). Otherwise, they express that the statement is true.

The past subjunctive after as if / as though indicates an unreal situation in the present. However, if the situation is true, we use a real tense to express present time:

He looks as if he

knew

the answer.

(he gives the impression that he knows the answer, but he (probably) doesn't know or we don't know whether he knows or not)

He looks as if he

knows

the answer.

(he knows the answer)

If we put the verb preceding as if / as though into the past tense, the present simple knows changes into past simple, whereas the past subjunctive knew stays the same. Therefore, both sentences will read as follows:

He

looked

as if he

knew

the answer.

Consequently, the meaning of this sentence (whether he knew the answer or not) can only be deduced from the context.

The past perfect subjunctive after as if / as though is used to refer to an unreal past situation. If the situation is true, we use a real tense to express past time:

He seems as if he

hadn't slept

for days.

(it seems that he hasn't slept for days, but he (probably) has or we don't know whether he has or not)

He seems as if he

hasn't slept

for days.

(he hasn't slept for days)

If the preceding verb is put into the past tense, the present perfect hasn't slept changes into past perfect, while the past perfect subjunctive hadn't slept stays the same:

He

seemed

as if he

hadn't slept

for days.

Quotes:

Most of us spend our lives as if we had another one in the bank. - Ben Irwin

Parents often talk about the younger generation as if they didn't have anything to do with it. - Haim Ginott

Live every day as if it were going to be your last; for one day you're sure to be right. - Harry "Breaker" Harbord Morant

As if you could kill time without injuring eternity. - Henry David Thoreau

Related topics:

Past perfect subjunctive

Past subjunctive

Second conditional

Third conditional