A more thorough explanation:

The all-or-nothing rule is a legal principle that states that if a class gift is invalid in part, then it is invalid in its entirety. This means that even if a class member's interest in the gift vests within the legal time limit, it can still be invalidated if another class member's interest is subject to partial divestment.

Let's say that a wealthy individual creates a trust fund for their grandchildren, with the stipulation that the funds will be distributed equally among all grandchildren when the youngest turns 25 years old. However, if any grandchild dies before turning 25, their share will be divided among the surviving grandchildren.

If one of the grandchildren dies before turning 25, their share would be divided among the surviving grandchildren. However, if the trust fund was created in a jurisdiction that follows the all-or-nothing rule, the entire gift would be invalidated because it is subject to partial divestment.

Another example could be a will that leaves a gift to "all of my nieces and nephews." If one of the nieces or nephews is deemed ineligible to receive the gift due to the all-or-nothing rule, then the entire gift would be invalidated.

These examples illustrate how the all-or-nothing rule can have significant consequences for class gifts, even if some class members are eligible to receive their share of the gift.