The name is a stats pun. It’s also the whole philosophy.

People assume “Priorsum” is one of those made-up startup words a naming agency spits out after a long weekend. It isn’t. It’s two very deliberate pieces of math stuck together, and if you know what they’re pointing at, you already know how the whole system thinks.

Break the word in half

Say it slowly and it splits where you’d expect: prior + sum. Both halves are borrowed straight from Bayesian statistics, which is a fancy way of describing something deeply ordinary, how a sensible person changes their mind when new facts show up.

Start with a prior

A prior is your honest starting guess, the belief you walk in with before you’ve seen today’s data. Most trading systems pretend they don’t have one. They present every call as if it were handed down from nowhere. We wanted the opposite: a system upfront about the fact that it always begins with an assumption, and is never too attached to it.

Then sum the evidence

The sum is where the personality lives. Every trade that closes is a little piece of evidence, and priorsum adds it to the pile. Enough evidence pointing the same way, and the belief moves. That’s the whole loop in a sentence: hold a view, gather results, let the results push the view around. The Σ on our logo is the summation sign, and yes, we chose it on purpose.

So, the short version

Priorsum is a bet that the best way to trade isn’t to be right on day one, it’s to be a little less wrong every day after. Start somewhere reasonable. Add up what actually happened. Update. Repeat, forever, without getting precious about the belief you started with. The name just says that out loud, in the shortest way we could manage, with a wink to anyone who caught the Σ.