Trust has no obligation structure because the trusted party assumes no binding duty

Evidence

If we reject such an analysis, we may still suppose that competent people who make promises thereby assume some obligation, which, however, may fall short of actually requiring them to keep all their promises. With trust, however, we cannot even formulate an analog of either the conventional or the logical account of an obligation. It is I who promise and who thereby assume an obligation. But, if it is I who trust, it is the trusted who would have to be burdened with an obligation. — Russell Hardin, Trust and Trustworthiness, 331

Categorization

• DEEPTHINKING: This asymmetry — promise burdens the promisor, while trust burdens the trusted without their consent — is a genuinely dense structural insight about why trust can never be codified the way promises can, directly relevant to the blindness scenario where the wife’s unasked-for sightedness burdens her with an obligation no one agreed to.
• ADDENDUM: Clarifies the structural difference between voluntarily assumed obligation and the imposed burden of being trusted — parallels the ‘On Sacrifice’ theme of obligations imposed without consent.