"If you don't know about something", then you must not believe or disbelieve it.
As if belief is necessary for knowledge, then belief must occur before knowledge of something's occurrence can occur.
That's why belief must occur before any knowledge of the truth and reality can occur.
Actually to be more specific; a believing mind gives an occurrence a way and place to occur. That's why QM demonstrates that observation and measurement is necessary and entailed in all occurrences, including wave function collapse and entanglement.