§ 112 Double Personality
It often happens that a single human being possesses a double personality. He is one man, but two persons. Unus homo, it is said, plures personas sustinet. In one capacity, or in one right as English lawyers say, he may have legal relations with himself in his other capacity or right. He may contract with himself, or owe money to himself, or transfer property to himself. Every contract, debt, obligation, or assignment requires two persons; but those two persons may be the same human being. This double personality exists chiefly in the case of trusteeship. A trustee is, as we have seen, a person in whom the property of another is nominally vested, to the intent that he may represent that other in the management and protection of it. A trustee, therefore, is for many purposes two persons in the eye of the law. In right of his beneficiary he is one person, and in his own right he is another. In the one capacity he may owe money to himself in the other. In the one capacity he may own an encumbrance over property which belongs to himself in the other. He may be his own creditor, or his own landlord; as where a testator appoints one of his creditors as his executor, or makes one of his tenants the trustee of his land.276 In all such cases, were it not for the recognition of double personality, the obligation or encumbrance would be destroyed by merger, or confusio as the Romans called it, for two persons at least are requisite for the existence of a legal relation. No man can in his own right be under any obligation to himself, or own any encumbrance over his own property. Nulli res sua servit.277