Consider these sentences:
1. The Mohawk hardly feels the scalping-knife while he shouts his death song.—Macaulay.
2. No success is worthy of the name unless it is won by honest industry and a brave breasting of the waves of fortune.—Huxley.
3. That country is the fairest which is inhabited by the noblest minds.—Emerson.
If we separate each of these sentences into its two propositions and apply the test,—which proposition is by itself grammatically complete? we shall see that the first proposition in each sentence is independent and the second dependent. But it may be said that in each case the dependent proposition is necessary for the truth of the sentence, that its thought must have been in the author’s mind not as an addition to the main thought but as something indispensable. This is perfectly true; logically the truth of the independent proposition does depend on the thought in the dependent proposition, but grammatically the dependence is the other way. Notice that in each of these sentences the second proposition denotes a modifying circumstance of the main thought, and therefore takes rank in the sentence merely as an idea,—telling in the first sentence when the Mohawk hardly feels the scalping knife, in the second under what condition success is unworthy, in the third which country is the fairest. Now, had the author so chosen, these modifications might all have been expressed by phrases, though possibly not so clearly.
Tests for Independent and Dependent Propositions.—From the foregoing we may deduce the following tests for propositions.
1. For the independent proposition.—(a) It contains the main thought that the author wished to convey. (b) It is so expressed that it is grammatically complete when standing alone.
2. For the dependent proposition.—(a) It expresses a modifying thought of some word or words in the independent proposition. (b) It may be changed to a simpler element, a word or phrase, provided there is a word or phrase in the language to express the same meaning. (c) It is not so expressed that it would make sense standing alone.
Function of the Dependent Proposition.—From what has already been said it may be inferred that the dependent proposition is employed (1) for variety, in the place of a word or phrase, (2) for the adequate expression of what we have no word or phrase capable of saying. But this is not all. Every dependent proposition can be changed into an independent proposition, and so might have been brought into the sentence in that form. For example,—
The Mohawk shouts his death song, and he hardly feels the scalping knife.