There was one time when I met someone new and I was certain that I had met her before. Eventually, I realized that I had seen her in a Zoom call, so her face was sort of familiar, but we had never actually met.

Brains can be weird. I have feelings that accompany thoughts, and these feelings of uncertainty or familiarity or fear help me make good decisions. I needs those emotions in order to act rationally.

But certainty is odd: it can function as an emotion, but it’s fallible. Even if I feel absolutely certain of something, that doesn’t necessarily make it true. I can misremember things. I can have an incomplete understanding. I might simply be wrong, no matter how certain I feel. (Certainty might also be thought of as a statistical principle, similar to confidence.)

I really hate uncertainty. I like to assume I know things that I really don’t. I jump to conclusions and run away from uncertainty as quickly as I can.

So what is actually certain in life? I know I exist and that my family exists and the world exists; I am certain about what I see and hear and feel. I am certain about many ideas that I have learned over the years.

But I think I could doubt everything in my existence if I really wanted to and be uncertain about everything.

So maybe being certain is just making a leap of faith based on fundamental assumptions so that I can keep making decisions in life. Certainty is merely convenient and useful: it helps lead to efficiency so that I can process the world and act quickly.

(Some of these thoughts came from reading The Tale of the Dueling Neurosurgeons: The History of the Human Brain as Revealed by True Stories of Trauma, Madness, and Recovery by Sam Kean.)