To think, to be of a certain opinion. The N.E.D. gives examples 1598, 1609, 1628, &c.

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1824.  [He bowed] so low, I opine I heard his brains rattle.—The Microscope, Albany, Feb. 28.

2

1824.  It may be well, I opinion, to notify, &c.—John Neal, ‘Brother Jonathan,’ 136.

3

1830.  Not a few leeches in that city, we opine, will vote for him.—Northern Watchman (Troy, N.Y.), Aug. 17.

4

1840.  “Didn’t I?” exclaimed Fog; “I opine I did; unequivocally I fancy I did.”—John P. Kennedy, ‘Quodlibet,’ p. 166 (1860).

5

1842.  

        “What care I for the red moonrise?
        Far liefer would I sit,”
we humbly opine is rank twaddle.—Phila. Spirit of the Times, March 2.

6

1842.  [Gen. Winfield Scott] had better keep his fingers to scratch his own ears with, we opine.—Id., Aug. 27.

7

a. 1854.  Do we know that for a certainty? We do not, as I opine.—Dow, Jun., ‘Patent Sermons,’ iv. 16.

8

1854.  We opine that he would have carried with him … prayers and good wishes.—Weekly Oregonian, Oct. 7.

9

1855.  We ‘opine’ the Rev. Sidney Smith does not ‘cotton to’ poodles more than we do.—Knick. Mag., xlvi. 206 (Aug.).

10

1857.  The word “light-house” we opine, means the same thing.—San Francisco Call, Jan. 21.

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