Moral certainty is when you know something is right or wrong, even though you don't have all the facts. It's like being sure something is true, even if you don't have proof. It's often used to describe people's beliefs about right and wrong, so that they're sure something is right or wrong even if other people don't agree. For example, someone might be morally certain that it's wrong to hurt other people, even if society or the law allows it.