Every man should be Mentally honest.
He should preserve as his most precious jewel the perfect
veracity of his soul.
He should examine all questions presented to his mind, without
prejudice, — unbiased by hatred or love — by desire or fear. His
object and his only object should be to find the truth. He knows,
if he listens to reason, that truth is not dangerous and that error
is. He should weigh the evidence, the arguments, in honest scales
— scales that passion or interest cannot change. He should care
nothing for authority — nothing for names, customs or creeds —
nothing for anything that his reason does not say is true.
Of his world he should be the sovereign, and his soul should
wear the purple. From his dominions should be banished the hosts of
force and fear.
Robert Green Ingersoll – “Truth” (1897)