Do not believe in anything simply because you have
heard it.

Do not believe in traditions because they have been
handed down for many generations.  Do not believe in
anything because it is spoken and rumored by many.

 Do not believe in anything simply because it is found
written in your religious books.  Do not believe in
anything merely on the authority of your teachers or
elders.  

But after observation and analysis, when you
find that anything agrees with reason, and is
conducive to the good and benefit of one and all, then
accept it and live to it.
-The Buddha, in the Kalama Sutra-