The important point is the use to which the facts are to be put. Before we act upon a fact or mak it the basis for a decision, we do need to check it. So we assess which of the believed facts could be useful and then proceed to try and verify it. For example, if the believed quietness of the Boeing 757 is vital to the siting of an airport thenwe certainly need to take that from the “believed” status to the “checked’ status.