The complex sentence with an adverbial clause of purpose

§ 173. Clauses of purpose generally express the purpose of the action, which is stated in the main clause. The verb-predicate in the subordinate clause is in the subjunctive mood as it expresses a planned but not a real action. Adverbial clauses of purpose are introduced by conjunctions that, so that, lest, so as, so, in order that, for fear that.

I trode on an edging of turf that the crackle of the pebbly gravel might not betray me.

I tell you all this so that you may understand me perfectly.

The conjunctions lest and for fear (that) introduce clauses stating what is to be prevented, as botli the conjunctions have a negative meaning. Lest is now extremely formal and after this conjunction the analytical subjunctive with should auxiliary is generally used.

He was like a man who is afraid to look behind him lest he should see something there which ought not to

be there.

“It’s a bit lighter in the park,” he said, “but take it (an electric torch) for fear you get off the path.”

In some cases the meaning of purpose in clauses introduced by lest and for fear that is weakened so that the clause expresses rather general motivation than purpose,or else an outcome of the action in the main clause, as in:

Lest the wall should collapse, they evacuated the building. (They did not evacuate the building with the

purpose of causing the wall to collapse.)

Better chain up the dog for fear he bites.

Note:

The conjunctions that, so that, lest, so are not confined only to clauses of purpose: that may introduce subject clauses, predicative clauses, and object clauses;

so that may introduce clauses of result, lest - clauses of cause, subject clauses, predicative clauses and object clauses; so - clauses of result and of cause.

The complex sentence with an adverbial clause of cause

Adverbial clauses of cause (or causative clauses) express the reason, cause, or motivation of the action expressed in the main clause or of its content as a whole.

Causative clauses may be introduced by the conjunctions as, because, since, so, that, lest, seeing (that), considering; or by the composite conjunctions for the reason that, in view of the fact that, in so far as (insofar as), by reason of. Of these the conjunction as is preferable when the sentence opens with a clause of cause.

As he was tired he preferred to stay at home.

Since there is no help, let us try and bear it as best we can.

They went down arm-in-arm - James with Imogen, because his pretty grandchild cheered him.

In so far as it is difficult to assign an external cause to certain happen­ings, they are written off as

uncaused or spontaneous.

As can be seen from the above examples, the causative clause may stand in preposition to the main clause, or follow it. It may also be embedded within the main clause, as in:

She loved to give, since she had plenty, and sent presents here and there to Lilian, the children, and

others.

Each of the conjunctions and conjunctive phrases expresses a certain shade of causative meaning, and so they are not always interchangeable. Because usually introduces clauses with the meaning of real cause. This can be illustrated by the ability of because-causes (but not others) to be included in questions. Thus it is correct to say:

Did you ask him because he was famous or for another reason?

But it is wrong to say: Did you ask him since he was famous...?

Unlike because, the conjunctions since and as introduce clauses with an explanatory meaning, or else that of motivation.

Since you are here, we may begin our talk.

The other reason why causal conjunctions, though synonymous, are not always interchangeable with because, is that some of them are polyfunctional: as and since may be conjunctions of time, as well as of cause. For example:

His mood changed as they marched down to the clocks, (temporal relation)

Note 1:

Causative relation may be found in compound sentences with the coordinating conjunction for. Its coordinate character is unmistakably shown by the fact that the clause with for cannot stand before the other half of the sentence.

Note 2:

Some causative conjunctions (as, because) may connect their clause to the main clause rather loosely, in which case the relation between the clauses is similar to coordination (such clauses may even be independent sentences). The causative clause generally expresses some grounds on which we can judge of the truthfulness of some idea expressed in the main clause, as in:

He was, I presume, a relative of the coachman’s, as he lay atop of the luggage, with his face towards the

rain.

Here the subordinate clause as he lay atop of the luggage, with his face towards the rain, does not express the cause, but gives some grounds which serve to prove the truthfulness of the supposition expressed in the main clause.

I must have been very weak at the time; because I know, after the first half hour or so, I seemed to take

no interest whatever in my food.

In this sentence the first clause is separated by a semicolon, which is not typical of subordination and is a mark of loose connection.

In colloquial English a clause of cause may be joined rather loosely to a sentence which cannot be its main clause: Are you going to the post-office? - Because I have some letters to post. (I ask you this because I have some letters to post.)