In economic forecasting, it is standard practice to project a range of possible outcomes, from the best to the worst case with the most likely somewhere in between.
In the independence debate, the separatists have consistently claimed that the best case scenario is what will actually happen. They portray this as 'making a positive case'.
Should any opponent point out that the most likely outcome is actually considerably worse than than this, he is accused of 'negative campaigning', whilst anyone who has the temerity to suggest that the worst case is every bit as likely as the best case is guilty of 'disgraceful scaremongering'.
The tone of the debate would be improved if everyone accepted that in the real world things do not always go as we wish them to go and other people do not necessarily agree with our view of what is in their best interests. Any sensible person hopes for the best but prepares for the worst.
It is a statement of the obvious that the single minded pursuit of a new prize may very well lose us prizes that we have already won.