In a utilitarian assessment of our various dealings with another we can commonly suppose that the interactions are more or less decoupled from all else, and we can simply choose according to what's best for the pair of us. In standard mutual trust interactions, I typically cannot justify cheating you on utilitarian grounds because I cannot judge that the pair of us is made better off on the whole unless we complete our exchange. We will know that the move from the status quo ante of no exchange to the condition of a completed exchange benefits both of us, so that it is better overall than not exchanging. If we cannot perform accurate interpersonal comparisons of utility, we cannot conclude that either of the outcomes in which I cheat you or you cheat me is better overall than the status quo ante of no exchange. Hence consummation of a mutual trust relationship is typically utilitarian, so long as it does not have substantial negative effects on others. A strong utilitarian commitment therefore generally implies a strong commitment to trustworthiness.

Russell Hardin, Trust and Trustworthiness, loc. 224