The purpose of the rule is to prevent property from being tied up for "perpetuity" (a very long time). The courts (and many people in society) do not want to hold property to see who will receive it after a complicated set of rules from the gift-giver. First, this would result in a waste of the courts' time and resources. Second, it would be a waste of the property that is being given through the gift. If a gift in a will violates the Rule against Perpetuities, the court will simply strike that gift and transfer the subject of the gift as if the will had not mentioned it.