What you know or think you know, is a mixture of what is fact and what you have been taught to accept as fact. When you follow the straight road, which is The Way, then you segregate fact from belief, and truth from that which is just believed to be true.
The follower clears his or her mind of things that have no basis in fact or reality, and distinguishes things that make sense from those that don't. Belief is based on a mixture of theory, fantasy and misguided conclusion. When fed to you as fact, your ability to reason is overridden, due to the confusions caused.