Motivated reasoning describes how our beliefs shape our perception of the world, ensuring that we see things as we are rather than as they are.
When we add a belief to our arsenal, evidence for its truth begins to accumulate. Even if we are presented with evidence that contradicts these beliefs, we will interpret it in ways that support our current narratives.
Confirmation bias causes us to focus on information that confirms our beliefs while ignoring or distorting evidence that contradicts them. Part of this reasoning stems from our proclivity to treat ideas like possessions, things we want to keep at all costs.