Whenever we are confronted by surprising facts or unintended consequences of our actions, we are presented with a learning opportunity. But since we like to feel ‘in control’ of our lives, we often avoid or ignore these opportunities, choosing instead to defend our beliefs against the facts. We are so good at selecting the facts that confirm our beliefs, and ignoring or denying the others, that we have developed an enormous capacity for self-deception. If we keep it up long enough, we can no longer see the difference between fact and opinion; argument becomes a battle of competing opinions, where the strongest (or loudest) wins. Unless we have a healthy respect for truth and a deep sense of our own fallibility, we have no defense against this kind of self-deception. Nor do we have any defense against those who would manipulate our beliefs for their own purposes.
Truths can be expressed only with symbols – and our ability to use symbols gives us the ability to lie. ‘A symbol is defined as a sign which is fit to serve as such simply because it will be so interpreted,’ but since our actual reading of any linguistic symbol is crucially governed by our language-using habits, symbols are ‘particularly remote from the Truth itself’ (Peirce, EP2:307). How informative symbols are for us depends on how they relate to the reality beyond our habits. When we recognize patterns in nature well enough to anticipate (with some degree of accuracy) what will happen in a given situation, we are tuned in to the habits of nature itself – of which human habits are a small and subordinate part, though crucial for humans. Our most systematic way of arriving at common beliefs about natural patterns is the communal quest we call science. But scientific method is just a more rigorous and public version of our common-sense way of critically assessing our own beliefs about the world.