# Theorem

A theorem is a statement that has been proved, or can be proved.

Derek Rayside was talking about how the only things that don’t decay are theorems. Everything material will one day disappear.

I also saw this in SE212 when looking at the definition of SE212 when looking at the definition of Semantics. We call:

**Goals**if we aren’t yet sure they are valid or proven**Theorems**if they have been determined to be valid or been proven

Occasionally, goals/theorems are referred as “sequents” or “problems”.