How to Update Your Beliefs

There's a word that we keep hearing more and more, in many perspectives of our lives: uncertainty.

How do we deal with uncertainty? Well, you could just shrug your shoulders and avoid making any decision, but the truth is, pretty much every single decision in our lives involves a different degree of uncertainty, but it rarely is zero.

There is, fortunately, a tool to help us navigate uncertainty. And it's called Bayes Theorem.

Bayes theorem is a very useful tool to update your beliefs. In a very simplified way, it says "What are the chances of X being true, given Y?" — for example, given that you're from Portugal, what are the chances of you liking football? What makes this powerful is that if you change the probability of liking football to a Portuguese person, then the final answer is different.

Let's play this example out to see how your answer changes and you update your beliefs.

As a starting point, you know Ronaldo is a football player from Portugal, and that he is very popular in his country. So, just with this data, you'd say that the probability of a Portuguese person liking football is more than 50%. Now, if you saw a news article that says that the most watched TV program of all time in Portugal was a football match, you'd update your answer, and say that maybe the chance is actually over 70%. You just updated your prior beliefs using new data.

For this to be useful as a tool, you'll need to be OK with changing the prior belief. If you're not, then the answer never changes. In other words, when people are 100% stuck in the way they think, they'll never change their opinion, and hence it's not worth discussing with them.