We shall discuss in this chapter some uses of marks determined partly by reason and partly by convention. In a subsequent chapter we shall take up the purely conventional uses of marks.
Among the commonest uses of marks is that of a comma before the conjunction that introducing a group of words. Our next two examples illustrate two classes of sentences in which “that” connects the parts of each sentence somewhat differently, permitting a difference in punctuation. As such modes of punctuation are not well settled by practice, and cannot be determined by reason, the use or omission of the comma in the second sentence (No. 40) becomes a matter of taste. We prefer the comma:
39. The court holds that the evidence is material.
40. The truth is, that we very much exaggerate the power of riches.
If it be said that punctuation which is a matter of taste necessarily becomes inconsistent punctuation, we may reply that some inconsistency in such punctuation does not in the least affect the value of the proper use of marks where they have real worth. A discussion of these seemingly minor points bears this value, that it may show niceties in grouping overlooked in our discussion of sharply defined groups.
No comma is required after “holds” in No. 39 because there is no grouping of words in the sentence that requires to be made in order to show a relation different from the relation that exists in the simplest form of expression, such, for instance, as the relation of adjective to noun, noun to verb, verb to object, etc.
In Sentence 40 “that” does not grow out of or coalesce with “is” as “that” grows out of and coalesces with “holds” in No. 39. The reader almost invariably pauses after “is” in such relations, as if to group into a whole what follows, such whole constituting the predicate of the sentence. The comma serves to show a grouping that is at once natural and helpful in reading, whether aloud or silently. This relation, with the need of the grouping, may be shown somewhat more clearly in a sentence where the use of the comma is quite unquestioned by good writers:
41. The benefit of a right good book depends upon this, that its virtues just soak into the mind, and there become a living, generative force.
Let us note that the relation here marked by a comma is quite suggestive of two similar relations which we indicated, respectively, by a colon (Sentence 26-3) and by a comma and dash (Sentence 34). It is plain that the relation in each of the three sentences (Nos. 26-3, 34, 41) is that of apposition; but it takes a different form in each, and so we punctuate the three sentences differently, each sentence falling into a different class.
While the above sentences present no difficulty in their punctuation, the punctuation of other sentences quite like them seems to be somewhat puzzling, yet it is based upon reason.