A valid express trust exists only where three conditions are satisfied: the settlor’s words must be imperative (certainty of intention), the property to be held on trust must be identifiable (certainty of subject matter), and the intended beneficiaries must be ascertainable (certainty of objects). These are the three certainties of a trust, drawn from Lord Langdale’s judgment in Knight v Knight (1840) and still the foundational test in common law jurisdictions today.1Cambridge Core. The Three Certainties Required to Declare a Trust – Or Is It Four? Distributional Certainty If any one of them fails, no trust arises, and the person you thought was your trustee may end up owning the property outright.
The case itself involved a will directing that estates pass through the male line and adding that the testator “trusted to the liberality” of his successors to reward old servants and tenants “according to their deserts.” Lord Langdale held that no trust had been created. The language was too soft, the property too vague, and the beneficiaries too indistinct.2National Case Law Archive. Knight v Knight (1840) 49 ER 58 From that failure, he built the test that carries his reasoning forward.
Certainty of Intention
The person creating the trust must have intended to impose a legally binding obligation, not merely expressed a hope. Courts look at the language in context. As Lord Langdale put it, the question “never turns upon the grammatical import of words” alone; the subject matter, the parties’ situation, and the probable intent all matter.2National Case Law Archive. Knight v Knight (1840) 49 ER 58
Words like “I wish,” “I hope,” “I have confidence that,” and “I desire” are called precatory language, and courts treat them with suspicion. In Re Adams and the Kensington Vestry (1884), a testator left property to his wife “in full confidence that she would do what was right” for their children. The Court of Appeal found no trust. Cotton LJ reasoned that the testator meant a moral obligation, not a legal one, and that earlier authorities had gone too far in reading vague hopes as binding directions.
The bar for intention is not impossibly high, though. No magic words are required. In Paul v Constance (1977), a man told his partner repeatedly that “the money is as much yours as mine” about an account held in his sole name. The Court of Appeal held those informal words were enough to create an express trust because, taken with how the couple used the money, they showed a present intention to share ownership. Formality is not what matters. Genuine intention is.
Certainty of Subject Matter
The trust property must be identifiable. If a court cannot pin down exactly what assets are held on trust, the trust fails. In Knight v Knight, the instruction to “reward” servants and tenants said nothing about which property or how much of it should be used.
Palmer v Simmonds (1854) is the classic example of vague subject matter. A testatrix directed her nephew to leave “the bulk of my said residuary estate” to named relatives if he died without children. The court struck the gift down. “Bulk” meant the greater part but not all, and no one could work out what definite portion was intended.
Hunter v Moss (1994) added an important qualification for intangible property. A declaration of trust over 50 out of 1,000 identical shares in a company was upheld even though the specific 50 shares were never segregated. Because shares are fungible, the court found the subject matter sufficiently certain. The same reasoning would not save a trust over 50 out of 100 paintings, where each item is unique. The practical takeaway for anyone declaring a trust over money or pooled assets: earmark a specific amount or open a separate account rather than trying to carve out “part of” a mixed fund.
Certainty of Objects
The beneficiaries must be ascertainable. A court needs to know who can enforce the trust, and a trustee needs to know who they owe duties to. In Knight v Knight, “old servants and tenants” rewarded “according to their deserts” failed on both counts: it was unclear who qualified as “old,” and the discretion built into “deserts” made individual shares impossible to determine.
The test differs by trust type. For a fixed trust, where each beneficiary takes a set share, the court must be able to compile a complete list of every beneficiary. This is the list certainty test from IRC v Broadway Cottages (1955). If you cannot draw the full list, the trust fails.
For a discretionary trust, where the trustee chooses how much each beneficiary receives, the test is looser. McPhail v Doulton (1971) replaced the list requirement with the “is or is not” test: the trust is valid if it can be said with certainty whether any given person is or is not a member of the class. You do not need to name every possible beneficiary, but the criteria for membership must be conceptually clear.
The distinction between conceptual and evidential uncertainty matters here. Conceptual uncertainty means the class definition is inherently vague, such as “my good friends” or “deserving people.” That kind of uncertainty kills both fixed and discretionary trusts. Evidential uncertainty means the definition is clear in principle but proving who fits it may be hard in practice. Evidential uncertainty on its own will not invalidate a discretionary trust after McPhail v Doulton.
Charitable Trusts Are Treated Differently
Certainty of objects, in the form described above, does not apply to charitable trusts. A charitable trust benefits the public or a section of the public, and enforcement falls to the state attorney general rather than to named individuals.3Legal Information Institute (LII) / Cornell Law School. Definite Trust Beneficiaries A trust “to feed the hungry” in a given region would fail as a private trust but can stand as a charitable one. Certainty of intention and certainty of subject matter still apply.
What Happens When a Trust Fails
Property from a failed trust does not vanish. In most cases a resulting trust arises by operation of law, returning the property to the settlor or, if the settlor has died, to their estate. Equity will not let the intended trustee keep the property free of obligation when the settlor plainly did not mean to give it to them outright.4Legal Information Institute (LII) / Cornell Law School. Resulting Trust
Knight v Knight itself went the other way, and the distinction is worth holding onto. Because the court found the testator meant an absolute gift to his brother with only a precatory wish attached, there was no failed trust to unwind. Thomas kept the property outright. A resulting trust arises where the settlor did intend a trust but the trust fails for uncertainty of subject matter or objects. Where the language is merely precatory, no trust was ever attempted, and the recipient keeps the property as an outright gift.
How the Three Certainties Appear in US Law
The three certainties began in English equity, but they now sit in statute across much of the common law world. In the United States, the Uniform Trust Code, adopted in some form by a majority of states, requires that a trust be created only where the settlor indicates an intention to create the trust, the trust has a definite beneficiary (or falls within a recognized exception for charitable or limited-purpose trusts), and the trustee has duties to perform.5Uniform Law Commission. Uniform Trust Code Section-by-Section Summary A beneficiary is “definite” if their identity can be ascertained now or in the future. Those statutory requirements map onto Lord Langdale’s framework: intention, identifiable property, and ascertainable beneficiaries.
The UTC also lets a trustee select beneficiaries from an indefinite class, but if the power is not exercised within a reasonable time, it lapses and the property passes as if the power had never been granted. That echoes the common law rule that uncertainty about who benefits cannot linger forever. A test built by a judge in 1840 now sits in black-letter statute, and the analysis a court runs on a modern trust document is essentially the one Lord Langdale set out.