I’m confident all four of our cats know that what prevents them from getting all the food or treats they want are opposable thumbs. Then they could pop open the lids on the containers.
Years ago, my brother had a big gray cat he called Buzz (due to his loud purring) who understood how a doorknob worked. You could tell from the scratches on the hallway’s handrail; Buzz was hopping up there and then trying his damnedest with his front paws while digging in with his rear claws for balance/traction. If he had thumbs, he would’ve had free reign of Grandma’s house and gradually warmed his way into her heart.