Noun
State of being doubtful.
Uncertainty of meaning; ambiguity; indefiniteness.
Uncertainty of event or issue.
Source: Webster's dictionaryThe most irresistible compulsion for me is that of doubt. I have doubts about all, including my own doubtfulness. I believe little, and that not fully. Scepticism is for me not a "fine art" but an integral part of my existence. Karlheinz Deschner
Since sounds have no natural connection with our ideas ... the doubtfulness and uncertainty of their signification ... has its cause more in the ideas they stand for than in any incapacity there is in one sound more than another to signify any idea. John Locke
the dubiousness of his claim Source: Internet
there is no question about the validity of the enterprise Source: Internet