It is not difficult to see why the construction of sentences consisting of two propositions is open to an amount of latitude which is not admissible in the construction of single propositions. As long as the different parts of a complex idea are contained within the limits of a single proposition, their subordinate character is easily discerned. When, however, they amount to whole propositions, they take the appearance of being independent members of the sentence.
[§ 556]. The concord of number.—It is believed that the following three rules will carry us through all difficulties of the kind just exhibited.
Rule 1. That the verb agrees with the subject, and with nothing but the subject. The only way to justify such an expression as the wages of sin is death, is to consider death not as the subject, but as the predicate; in other words, to consider the construction to be, death is the wages of sin.
Rule 2. That, except in the case of the word there (p. [434]), the word which comes first is always the subject, until the contrary be proved.
Rule 3. That no number of connected singular nouns can govern a plural verb, unless they be connected by a copulative conjunction. The sun and moon shine,—the sun in conjunction with the moon shines.
[§ 557]. Plural subjects with singular predicates.—The wages of sin are death.—Honest men are the salt of the earth.
Singular subjects with plural predicates.—These constructions are rarer than the preceding: inasmuch as two or more persons (or things) are oftener spoken of as being equivalent to one, than one person (or thing) is spoken of as being equivalent to two or more.
Sixpence is twelve halfpennies.
He is all head and shoulders.