A hoteliers' association certifies each of its member lodges as clean, and its handbook explains that a lodge is certified clean because it is clean, the association being unwilling to certify a lodge that is not. An answer to which of the following questions would be of most use in judging what the certificate is worth?

The handbook's explanation goes round in a ring: the lodge is clean because certified, certified because clean. What breaks the ring is some procedure outside it that could come out the other way, so the question to ask is whether any finding could cost a lodge its certificate and whether one ever has. If nothing could, the certificate records membership and not cleanliness. How many lodges belong tells us the association's reach; the year it began tells us its age; and whether visitors are guided by it tells us its influence — a worthless certificate may be old, wide and much relied on.