All books in this flagship series contain carefully selected substantial extracts from key cases, legislation, and academic debate, providing able students with a stand-alone resource. This chapter elaborates on the requirements of an express trust, which include certainty of intention, subject matter, and objects — referred to collectively as ‘the three certainties’. A trust requires that it be clear to which objects, whether people or purposes, the trustees can and cannot appoint the property. Also, there needs to be someone in whose favour the trustees, and in default, the court, can enforce the trust. This is known as the ‘beneficiary principle’. Certainty of subject matter is assessed objectively and problems may arise if the property is not clearly ascertained. Different tests are used to establish the certainty of objects: for a fixed trust, a complete list of beneficiaries is needed unless the trust is subject to a condition precedent. For discretionary trusts and fiduciary powers, it needs to be certain whether any given person is or is not within the scope of the class of objects.