PETER Wylie (Letters, August 17) takes Iain AD Mann (Letters, August 15) to task for thinking that an independent Scotland could cover its £9 billion deficit “quite easily by government borrowing”. But in so doing he treats what really are “known unknowns” (to quote Donald Rumsfeld) – what we know we don’t know – as “known knowns” – what we know we know (or in Mr Wylie’s case, what we think we know).

One example is why Standard Life would not buy into Scottish government debt. Since it considers itself a global business, even if “90 percent of its customers are in England”, it must deal in a whole range of global currencies. Yet according to Mr Wylie they would be deterred from investing in Scottish debt for currency reasons. Surely if the return is reliable and competitive, then investors would be happy to invest? The issue is not the currency in which they are paid, but the reliability of return, and in this regard, for the UK, even with the fall in the value of the pound since June 24, and the prospect of Brexit is informative as the UK is still able to sell gilts to manage its debt.

How much Scottish debt would be owned domestically is certainly a “known unknown”, but how is it that other small countries – or even some large ones – which do not have a financial services sector on the same scale as the UK, get by? Or is Scotland uniquely disadvantaged in this regard?

His final “known unknown” is that the cost of servicing debt for an independent Scotland would be “a lot higher” than for the UK government. Leaving to one side what “a lot higher” actually means, and more importantly whether the UK will continue for much longer to be able to finance its debt at present rates of interest, the premium on Scottish debt would depend on the scale of deficit we face on independence. Let’s suppose that is not before 2020. What will the price of oil be then? What level of UK debt would Scotland actually have to take on? If “known unknowns” exist, then these are examples.

In short, Mr Wylie in sketching out his severe, if not apocalyptic, view of the future, really does ignore Mr Mann’s core point, that if arguments, such as Mr Wylie’s, are to be redeemed then they really do have to be obliged to present evidence why an independent Scotland would be unable to address the challenges that every other small country does. Certainly presenting “worst case analyses”, such as Mr Wylie’s, singularly fails to do this.

Alasdair Galloway,

14 Silverton Avenue, Dumbarton.