fully vested interest, then divorce C without affecting his rights to Blackacre. Contingent remainders A contingent remainder is created when a remainder cannot fully vest at the time of granting. This normally occurs in two situations: when the property can't vest because the beneficiary is unknown (for example, if the beneficiary is a class subject to open), or when the property can't vest because the (known) beneficiary is subject to a condition precedent which has not yet occurred. Legislatures and courts tend to prefer vested remainders over contingent remainders, to reduce uncertainty in ambiguous grants, and to speed up probate. Executory interests An executory interest is a future interest, held by a third-party transferee (i.e. someone other than the grantor), which either cuts off another's interest or begins some time after the natural termination of a preceding estate. An executory interest vests upon any condition subsequent except the natural termination of the original grantee's rights. In other words, an executory interest is any future interest held by a third party that isn't a remainder. Executory interests usually arise when a grantor gives property to one person, provided that they use it a certain way. If the person fails to use it properly, the property transfers to a third party. There are two different types of executory interests: shifting and springing. Executory limitations transferring ownership from the grantor to a third party are called springing executory interests, and those that transfer from the grantee to a third party are called shifting executory interests. Shifting executory interest A shifting executory interest cuts short someone other than the grantor. For example, if O conveys property "To A, but if B returns from Florida within the next year, to B"; here, B has a shifting executory interest, and A has a fee simple subject to this shifting executory interest. A shifting executory interest may be premised on any event, irrespective of whether that event is under the control of one party or the other, or if it is an external event under the control of neither party. For example, a conveyance "To A, but if the property is ever used as a commercial dairy, to B" would leave A in control of the condition; so long as A does not use the property in the proscribed manner it will remain hers. Conversely, a conveyance "To A, but if B receives a law degree, to