doubtfulness

1. State of being doubtful.

2. Uncertainty of meaning; ambiguity; indefiniteness. « The doubtfulness of his expressions.» Locke.

3. Uncertainty of event or issue. Bacon.

noun

A lack of conviction or certainty: doubt, dubiety, dubiousness, incertitude, mistrust, question, skepticism, suspicion, uncertainty, wonder. See certain/uncertain.

The noun has 2 meanings:

Meaning #1: the state of being unsure of something
  Synonyms: doubt, uncertainty, incertitude, dubiety, dubiousness

Meaning #2: uncertainty about the truth or factuality of existence of something
  Synonyms: doubt, dubiousness, question