certainty — Certainty is the state of being definite or of having no doubts at all about something.
clarity — The clarity of something such as a book or argument is its quality of being well explained and easy to understand.
clearness — free from darkness, obscurity, or cloudiness; light: a clear day.
definiteness — clearly defined or determined; not vague or general; fixed; precise; exact: a definite quantity; definite directions.
lucidity — the quality of being easily understood, completely intelligible, or comprehensible: She makes her argument with pointed logic and exemplary lucidity.