Different kinds of disposition demand different degrees of precision about who the beneficiaries are, and choosing the wrong test is where most problems arise. This chapter starts with the requirement itself, separating conceptual from evidential certainty, before working through the complete list test for fixed trusts and the is/is not test for discretionary trusts. It then applies conceptual certainty to common class descriptions such as friends, relatives and employees, and adds the further hurdles of administrative workability and capriciousness, alongside the lighter rules for mere powers of appointment. Finally, it covers the duties of trustees holding discretions and powers, how far the court will intervene, and where the property goes — by resulting trust or under a gift-over — when a trust fails for uncertainty.
