 News of borderline status has an evidential character. Loss of clarity brings loss of warrant. If you do not lower your confidence, you are open to the charge of dogmatism. To concede that your ferry is a borderline case of ‘seaworthy’ is to concede that you do not know that your ship is seaworthy. That is why debates can be dissolved by showing that the dispute is over an absolute borderline case. The debaters should both become agnostic. After all, they do not have a license to form beliefs beyond their evidence. If your ferry is borderline seaworthy, you are not free to believe it is seaworthy. 