"All three of those methods are actually FAILPROOF ways of gaining knowledge, unless of course you doubt your own ability to gain knowledge in which case you may fail."

I see people every day that think their perception of truth is failproof. Many of them are full of delusion and self deception. Assuming your perception is foolproof is one of the easiest ways to get tricked. Because your perception itself can be tricked, as well as your intuition.