OLIVER WILLIAMSON has written an interesting and important article on an interesting and important topic.1 Economists' insistence that people can usefully be modeled as rational utility maximizers-as "calculative" beings, to use Williamson's term-is probably the single aspect of economics that noneconomists find hardest to swallow. All of us who work with economics have had to defend this approach in lunchtime conversations with colleagues or in classroom discussions with students. In his current article, Williamson addresses these concerns systematically and applies them to the important concept of "trust." In doing so, he displays a wide knowledge of the sociological literature on that topic and a commendable willingness to engage the sociologists on their own terms. As will soon become apparent, I agree with most of what Williamson has to say on this point. His analysis would be even more useful, however, if he distinguished between two different uses to which the term "trust" is sometimes put. The following examples will illustrate: (1) "X loaned some money to Y. What might explain X's act of trust?" (2) "X loaned some money to Y because he trusted her." In the first example, "trust" is used merely to label the behavior for which an explanation is being sought. In the second, "trust" is put forward as an explanation of that behavior. The next section surveys some of the authors who use "trust" in the