In both these estates the holder has a fee simple except that there is a limitation which may take his rights from him and give them to another. Both give the holder all the benefits of full fee ownership subject to the happening of a future contingency, which if it occurs ends his rights. In a fee upon condition the contingency may never arise, while in a fee determinable, it must arise, if at all, within a certain or determinable time. For example: A piece of land is given to be used as a church, the gift providing that if used for any other purpose the land shall revert to the giver or his heirs. In this case the fee of the land is in the church organization and may remain in it forever but will cease when the land ceases to be used for a church, in which event the fee would revert to A if living, or his heirs. The fee is upon condition. If land is given to A and his heirs with a provision that if A die leaving no children then the land shall go to B, A has a fee determinable. A has the full benefit as long as he lives. Within a certain time, that is, at A's death, the contingency must occur if at all. Either A leaves children or not. In either event the limitation on the fee is then determinable.