But if I am certain I do not possess the book, the reply is different; "I have not the book you mention; if I had, it should be at your master's service."
Both these forms of speaking are correct; but the question is, what is the difference? It cannot be in time; for both refer to the same. The ideas both respect present time; "If I have it now, it shall be at your master's service"—"If I had it now, it should be." The distinction in the meaning is universally understood, and is simply this; the first expresses uncertainty; the last implies certainty, but in a peculiar manner; for an affirmative sentence implies a positive negation; and a negative sentence implies a positive affirmation. Thus, if I had the book, implies a positive denial of having it; if I had not the book, implies that I have it: And both speak of possessing or not possessing it at this present time.
The same distinction runs thro all the verbs in the language. A man, shut up in an interior apartment, would say to his friend, "if it rains you cannot go home." This would denote the speaker's uncertainty. But on coming to the door and ascertaining the fact, he would say, "if it rained, you should not go;" or, "if it did not rain, you might go." Can these verbs be in past time? By no means; if it did not rain now, you could go, is present, for the present existence of the fact prevents the man from going.
These forms of speech are established by unanimous consent in practice.
"It remaineth that they who have wives, be as tho they had none, and they that weep, as tho they wept not; and they that rejoice, as tho they rejoiced not; and they that buy, as tho they possessed not."——1 Cor. vii. 29, 30.[116]
"Nay, and the villains march wide betwixt the legs, as if they had gyves on."——1 Henry IV.
"We have not these antiquities; and if we had them, they would add to our uncertainty."——Bolingbroke on Hist. let. 3.
"Whereas, had I (if I had) still the same woods to range in, which I once had, when I was a fox hunter, I should not resign my manhood for a maintenance."——Spect. No. 14.
"I confess I have not great taste for poetry; but if I had, I am apt to believe I should read none but Mr. Pope's."[117]—— Shenstone on Men and Manners.
Whatever these verbs may be in declaratory phrases, yet after the conditional conjunctions if and tho, they often express present ideas, as in the foregoing examples. In such cases, this form of the verb may be denominated the hypothetical present tense. This would distinguish it from the same form, when it expresses uncertainty in the past time; for this circumstance must not be passed without notice. Thus, "If he had letters by the last mail," denotes the speaker's uncertainty as to a past fact or event. But, "if he had a book, he would lend it," denotes a present certainty that he has it not. The times referred to are wholly distinct.