We have a proclivity to overestimate our abilities although there is so much truth that we don’t know yet.
We draw conclusions based on what we perceive as truth. The truth we believe may be skewed or outright false. But if we believe it is true, it is true until someone proves us wrong.
We also don’t like to listen to what contradicts our viewpoints. If you are convinced that being a vegetarian can save the earth, you tend to disprove the contradicting opinion. That makes it difficult for us to discover the fact.
Conviction can blind us to reality.