Sometimes people like to apply the knowledge they have today to some situation they had in the past. “Well, if only I knew about that then!” The phrase commonly used is “Hindsight is 20/20.” While this technique may scratch some mental itch, it is not productive because you can’t change the past.

I prefer different thought experiments that could be useful today or in the future. One such experiment is to think about something you know that you wish you didn’t know. Maybe it’s an image in your mind of something you saw that you wish you didn’t. Or perhaps it is something you overheard in conversation. 

How can this thought experiment be useful? After all, you can’t actively un-know something. Unless your memory fades or you are stricken by amnesia or have some type of shock therapy, the thoughts are here to stay. 

• If you think about why you wish you didn’t know something, it can help you understand yourself. Is it knowledge you really should have but you resisted it? This could be an opportunity to change your thinking. 

• If it is something that has been painful or harmful or disturbing, what is so disturbing about it? Is there anything you can do in the future to avoid being exposed to more of it, e.g., staying away from certain YouTube channels or even certain people.

• Imagining that other people have things they don’t want to know can help you increase empathy. Just because you have knowledge about someone or something doesn’t mean you need to share it with people. Put yourself in the other person’s shoes and think about whether you would want to have the knowledge from their perspective.

Think about something you know that you wish you didn’t know. How has it affected you? Can you turn it into a positive experience for you or someone else?