Irreversibility refers to the preoperational child's tendency to "believe that what has been done cannot be undone".
Irreversibility is a phase in early child advancement in which a kid erroneously trusts that activities can't be turned around or fixed. For instance, if a three-year-old kid sees somebody straighten a ball of play dough, he won't comprehend that the batter can without much of a stretch be changed into a ball. Kids regularly develop past this phase by age seven.
Manifest Destiny was the belief that settlers had the right to settle in the West. Therefore, they believed nothing had the power to prevent their settlement