No one can know how another human being will act in the future. Trust is a policy apt for conditions where knowledge is unavailable, as in the case of the free acts of another person (in Locke's view) it will always remain. Trust does not have to be any more credulous or sentimental than the judgement of those who decide how to allocate it, though it will in practice, naturally, not be any less so either.

XREF: Connects to the distinction between risk (probabilistic, calculable) and uncertainty (unquantifiable) from decision theory — trust sits in the latter domain.

Diego Gambetta, Trust - Making and Breaking…, loc. 1197