Reason makes facts intelligible.
Reason is a justified statement.
A fact is a thing of existence and/or actual occurance presented as objective reality (not subjective).
[To be] justified is [to be] characterized by definition.
A statement is a summary of activity or process of presenting (usu. publicly, orally and of oneself) and it is to make known; formally, officially, explicitly, evidently, emphatically, et al.
To define is to be definite. To be definite is to be certain and free of all ambiguity, uncertainty, or obscurity; to be unquestionable, indisputable, unopposed, or unable to be engaged in argument or debate.
Certainty is a specific character, quantity, or degree (state) of a quality.
Therefore, the best quality of reason is certainty and the best state of reason is definite.
~ Johnnathan Durtche