Aquinas distinguishes three mental states we often conflate: Knowledge, when something follows clearly from something certain, and once grasped isn't a matter of choice. Opinion, something arbitrarily chosen. Belief falls in between, it's neither arbitrary, nor held by necessity.
"Can you change your beliefs?" is one of my favorite questions to think about. Because like, not really. I can't decide to wake up tomorrow believing something different. But why not? It's just thoughts. Path dependency? The minds of my past selves constraining present me?