Knowing and doing are not the same thing. We think because we know a platitude we know how to practice it. “Treat others as you would want to be treated” seems simple enough, but as soon as we are stuck in traffic, having a bad day, or feel competitive, that platitude often goes out the window.
We assume once we learn something, which often means just reading or hearing it, we will remember and apply it in the world. Yet in the moment we respond to situations emotionally or based on habit, and our common sense gets left behind. Instincts often conflict with wisdom. And even if our judgement is sound, In the workplace or family those in power might not have common sense, making it harder for those who do have it to take action based on it. Our social nature and desire to feel safe often overrides good sense, or misshapes our perception of what is good.
There are many books about cognitive bias. These biases are documented blind spots in how our minds work, including things like confirmation bias, or the habit of finding the first piece of data that fits our argument and looking no further. Common sense, in the abstract, dictates we should look for data that both supports and rejects a theory, as that would force thinking about how to improve an opinion (instead of merely defending an old one). But we want to be right. And we want to be efficient. Both of which work against even this simple kind of common sense.
We also forget that common sense is always changing, sometimes progressing, sometimes regressing. There can be good reasons for defying common sense as that’s what progress will feel like. There’s also the reality that in uncommon situations, common sense might not apply. There can be nuances and contexts that demand we go against what in other situations we think is right.
A meta kind of cognitive bias is faith that knowledge of cognitive biases reduces your likelihood for having those biases. Since most cognitive biases are a side effect of how our brains function, awareness of them is often not enough to change our behavior. But we like to pretend it is. “Oh, I know about cognitive biases, so I’m immune to them now” is a fallacy. As G.I. Joe said, knowing is half the battle. The other half is often the harder one.
Common sense is not common practice. Knowing is not the same as doing. It can take months of effort to train yourself new habits for your behavior, work that no amount of knowledge can replace. For culture to develop a new kind of common sense can take a generation. Sometimes all we can hope to do is improve our humility, as completely avoiding mistakes and failures, even common ones, is beyond us.
Also see: Why it’s ok to be obvious.