The pronouns who, which, and that, are sometimes resolvable into and he, and she, and it. Mr. Harris, indeed, has said, that the pronoun qui (who) may be always resolved into et ille, a, ud (and he, and she, and it). This opinion, however, is not perfectly correct; for it is thus resolvable in those examples only in which the relative clause does not limit or modify the meaning of the antecedent. If I say, “Man who is born of a woman, is of few days, and full of trouble,” the relative clause is not restrictive; I may, therefore, resolve the pronoun, and say, “Man is of few days, and he is born of woman.” “Light is a body which moves with great velocity,” is resolvable into “Light is a body, and it moves with great velocity.” But when the relative clause limits the meaning of the antecedent, the relative is clearly not thus resolvable. “Virgil was the only epic poet, among the Romans, who can be compared to Homer.” The signification of the antecedent is here restricted by the relative clause: we cannot, therefore, by resolution, say, “Virgil was the only epic poet among the Romans, and he can be compared to Homer;” for the former of these propositions is not true, nor is the sentiment, which it conveys, accordant with the meaning of the author.
The pronoun what, if not employed interrogatively, is equivalent to that which; and is applicable to inanimate things only, as, “I believe what I see,” or “that which I see.”
What admits no variation.
The relative pronouns who, which, are often used interrogatively, and are, therefore, in such cases considered as interrogatives. When thus employed, it is the opinion of the author of the British Grammar, that they still retain their relative character. “The only difference,” says he, “is this, that the relative refers to an antecedent and definite subject, and the interrogative to something subsequent and unknown.” The example which he adduces in support of his opinion is the following: “Who first seduced them to that foul revolt?” “The very question,” says he, “supposes a seducer, to which, though unknown, the pronoun who has a reference.” Answer, “The infernal serpent.” He continues, “Here, in the answer, we have the subject, which was indefinite, ascertained; so that the who in the interrogation is as much a relative as if it had been said originally, without any interrogation at all. It was the infernal serpent who seduced them.” Others adopt an opinion diametrically opposite, contending that who and which are properly interrogatives, and that even, when used as relatives, they still retain their interrogative character. This theory a few examples will sufficiently illustrate.
“The man who?” (which man?) his character follows, “has no music in himself.”
“The city which? (what city?) Romulus built was called Rome.”
“Happy the man whose cautious feet.”
“Happy that man who? his (whose) cautious feet.”
“Light is a body which? (body) moves with great velocity.”