Perhaps there are a various shades of belief and that they are a subtle indication that the full truth is not known. If you know (e.g. in the present moment) then you don't need to hold a belief. Other than that, the degree of belief tends to be an assessment of probability, often about the past or future. Blind belief is where the critical faculties have been suspended, often as a result of earlier persuasion or indoctrination or through the need to satisfy a desire or mitigate a fear, sometimes the source of prejudices. I seem to remember that an older meaning of 'belief' was more associated with love/life (lief). 'Belief in God' then became 'be love/life in God' ... a state of union or a unitive 'knowing'.