Epicurean philosophy employs an empirical epistemology. The Epicureans believed that all sense perceptions were true, and that errors arise in how we judge those perceptions. When we form judgments about things ("hupolepsis"), they can be verified and corrected through further sensory information. For example, if someone sees a tower from far away that appears to be round, and upon approaching the tower they see that it is actually square, they would come to realize that their original judgement was wrong and correct their wrong opinion.