doubtless

epäilemättä Characterized by or experiencing no doubt at all, certain; undoubted; undoubting.
1880, B. Stewart and P. G. Tait, The Unseen Universe, Macmillan (London), p. xiii:

There are those who have doubtless faith in revelation.

It is doubtless that the old reprobate who sued for his daughter's hand heard some unsavory truths from the man.

Pretty child, sleep doubtless and secure.

I cannot remember that I spoke a word, though doubtless I did.

The men, Dorothy thought, were about as old as Uncle Henry, for two of them had beards. But the little woman was doubtless much older. Her face was covered with wrinkles, her hair was nearly white, and she walked rather stiffly.