reasonableness /ˈɹiː.zə.nə.bəl.nəs/ noun2 •The state or characteristic of being reasonable.This dictates the reasonableness of the rupture of a unipersonalist absolute that is pseudomonotheistic since, in this case, the possibility of any other being would have been made impossible. — 2004 •A reasonable action or behaviour. formsreasonablenesses