Here’s another chance to sharpen our grammatical tools. Is this sentence correct: he is one of those persons, who is always on time. We will need either two knives or one double-edged sword to examine this deceptively simple sentence, one blade for grammar and the other for punctuation.
When we revise our work, we should revise clause by clause, not sentence by sentence. Every clause (that is, a group of words with a subject and verb) is an assertion, which means its words must cohere in structure in order to say something, not necessarily something complete, but something both logically comprehensible and grammatically sound. Every clause we write asserts a thought, so when we revise by clauses, we give ourselves a chance to confirm both what we are saying and how one thought connects to another in the same sentence. Thus, a sentence has as many thoughts as it has clauses.
We remember that there are two kinds of clauses, independent and subordinate. The first clause in our example is independent (he is one of those persons), and the second is subordinate (who is always on time). Any clause which begins with a relative pronoun (here who) is by definition subordinate, and such clauses have the special designation of relative clauses. These relative clauses act most often as adjectives which modify the antecedent of the pronoun; this requirement will be material to our analysis as we proceed, because adjectives either define or describe their referent and each involves a certain punctuation.
A sentence with at least one independent clause and at least one subordinate clause is defined stylistically as a complex sentence. The independent assertion in our example intends simply to identify the subject, he, with a certain kind of person (one of those persons). Had the sentence ended there, we would certainly have wanted to know more about just what kind of person the subject he is. Logically, or sensibly, we could say that this independent clause is not complete, but grammatically it is, and so we are right to call it an independent clause. Still, any reader will want to know more, and here is where two difficulties arise with the example sentence as we have it.
The writer has placed a relative clause in the sentence to define the class of persons the subject of the independent clause belongs to: he is one of those persons. The relative clause then steps in to define those persons (not just one) as those who are always on time, but as we can see, the writer has used the singular verb is instead of the plural verb are. The antecedent of the relative pronoun who, in other words, is the plural noun persons (not one), and since who is representing persons in the relative clause, the verb of that clause must be plural to match the number of its subject. Verbs accord in number with their subjects.
A problem remains, though. We said that the relative clause here is defining its antecedent, persons. But when a relative clause (or any other element) is defining, and not simply describing, its antecedent, it is considered a restrictive clause, and such clauses are never set off with a comma. The function of a comma is to cut, to separate what is logically inessential or separable from something else. To define some word, however, is at the heart of logical clarity, and so the punctuation rule is to be met in order to keep the grammatical structure of the sentence in sound logical order. The correct version of our sentence then is: he is one of those persons who are always on time.
That might sound odd to our ears, but our ear responds to what it hears, not to what the structural requirements of the sentence are. The ear has its place, but at a much higher level of rhetorical design, where the thought and logic of clauses begin to blend into feeling and emotion. But that’s another story.
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