What is it about the €18bn deficit that Gerry Adams doesn't understand? The answer was blindingly obvious and deeply shaming for him: everything.
Experts might declare him to be a "deficit denier" but that description would suggest that his strong views are based on some experience or knowledge of the subject.
He sounded like an economic dunce speaking on LMFM radio in Louth and as the interview progressed listeners could add financial dunderhead to his shortcomings.
It was an amazing performance where Mr Adams's astonishing ignorance of the economic crisis made him leading contender for Bluffer Of The Year.
It wasn't the first time his stunted knowledge of finances and economics were exposed in public: he was humiliated in the televised mini-leaders' debate before the 2007 General Election.
Yet undeterred by his previously disastrous encounter with the dismal science, Mr Adams blithely offered to address economics again yesterday.
As a Dail candidate in Louth, the president of Sinn Fein's press office asked the local radio station to allow him reply to questions about his plans to deal with the economy.
The questioner couldn't understand Mr Adams's claims that Ireland can act unilaterally and pull out of the IMF/ECB bailout while renegotiating the terms.
The political editor of this newspaper had asked the questions and he further wondered why Mr Adams would not say if that was to happen and how he plans to fund the State.
Mr Adams is a Dail candidate and President of Sinn Fein, presumably he must know that his party voted for the bank guarantee -- and that the money owed to bond-holders is now sovereign debt.
It is hard to exaggerate the depth of Mr Adams's lack of knowledge about the crisis facing this country, but his ignorance, when spoken, is eloquent.
He is expected to win a seat on February 25 but others in the party must be quietly questioning the wisdom of him keeping his position as boss of bosses.
Sinn Fein's newest TD Pearse Doherty has been impressive in the media and the party is expected to at least double its representation in the Dail in the election.
The night before on 'The Frontline' programme, Mr Doherty taunted the other opposition parties, saying they couldn't wait to get into ministerial Mercs. It is clear that the party's strategy is to play as the outsiders and depict all the others as part of a cabal which Sinn Fein will not join.
But its economic policy seems to follow the model that beggared Argentina, and sanctions welshing on sovereign debt while taking on the ECB and IMF.
It is the sort of nonsense that was popular in student groups in the late 1960s, at the beginning of the Troubles. Mr Adams and some of the brain's trust that runs Sinn Fein were in their heyday back then and, like the Bourbons, they have learnt nothing and forgotten nothing.
Mr Adams is like some ageing prize-fighter who may have signed up for a fight too many and now dreads the build up to the showdown on February 25.
His career peaked when he stood with a Taoiseach, a US president, and a British prime minister to celebrate the Good Friday Agreement.That was nearly 12 years ago -- and prosperity was on its way to complement the peace.
And Gerry Adams is a wartime leader who doesn't understand prosperity or economics.