to doubt not but

Doubt \Doubt\, v. t.
   1. To question or hold questionable; to withhold assent to;
      to hesitate to believe, or to be inclined not to believe;
      to withhold confidence from; to distrust; as, I have heard
      the story, but I doubt the truth of it.
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            To admire superior sense, and doubt their own!
                                                  --Pope.
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            I doubt not that however changed, you keep
            So much of what is graceful.          --Tennyson.
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   {To doubt not but}.

            I do not doubt but I have been to blame. --Dryden.
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            We doubt not now
            But every rub is smoothed on our way. --Shak.
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   Note: That is, we have no doubt to prevent us from believing,
         etc. (or notwithstanding all that may be said to the
         contrary) -- but having a preventive sense, after verbs
         of "doubting" and "denying" that convey a notion of
         hindrance. --E. A. Abbott.
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   2. To suspect; to fear; to be apprehensive of. [Obs.]
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            Edmond [was a] good man and doubted God. --R. of
                                                  Gloucester.
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            I doubt some foul play.               --Shak.
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            That I of doubted danger had no fear. --Spenser.
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   3. To fill with fear; to affright. [Obs.]
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            The virtues of the valiant Caratach
            More doubt me than all Britain.       --Beau. & Fl.
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