to doubt not but

Webster's Dictionary (GCIDE)

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. [1913 Webster]

To admire superior sense, and doubt their own!— Pope.[1913 Webster]

I doubt not that however changed, you keep So much of what is graceful.— Tennyson.[1913 Webster]

To doubt not but.

I do not doubt but I have been to blame.— Dryden.[1913 Webster]

We doubt not now But every rub is smoothed on our way.— Shak.[1913 Webster]

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. [1913 Webster]

2.To suspect; to fear; to be apprehensive of. [Obs.] [1913 Webster]

Edmond [was a] good man and doubted God.— R. of Gloucester.[1913 Webster]

I doubt some foul play.— Shak.[1913 Webster]

That I of doubted danger had no fear.— Spenser.[1913 Webster]

3.To fill with fear; to affright. [Obs.] [1913 Webster]

The virtues of the valiant Caratach More doubt me than all Britain.— Beau. & Fl.[1913 Webster]