How do we know what we think we know? We have our direct experiences, the 2nd- to nth-hand stories we accept as truth, and what we, using our intellect, derive from those.
But there are problems with every part of that answer. We may or may not correctly understand our direct experiences. Believing what we hear from others is always chancy. And no matter how smart we think we are, our intellect doesn’t always come up with the right answer.
I think what we know is a lot more nebulous than most of us acknowledge. One should always question the validity of their worldview and be open to revising what they think they know, but that’s not common, especially as people get older.
But what, then, should be the basis of our actions? What can we do other than accept the vague mass of inchoate thoughts, half-formed concepts, and class, racial, and religious prejudices inside all of us as the basis of our worldview and our actions? After all, nothing says that we have to be right all the time or make the correct choices all the time. To be human is to be fallible, to be wrong sometimes, and to make bad choices.
One alternative is to abandon our reason and accept the dictates of those we consider to be our political or social or religious leaders as the gospel truth and let them tell us what to think and do. That’s the strategy adopted, consciously or not, by many. It’s painless, easy, and shoves the responsibility for our decisions onto others.