The only thing is, we've never been told officially what was wrong with him. And they're probably none the wiser today - officially, anyway - about what laid Ian Paisley low five years ago.
As David Gordon, the Belfast Telegraph's investigations correspondent, describes it in his new book on the coup that levered the reins of power from Ian Paisley to Peter Robinson, the Democratic Unionist Party is run on the principle of 'need to know' - and if you don't need to know, you won't.
Even Peter Robinson and Nigel Dodds - two of the party's most senior figures and close confidants of Ian Paisley in 2004 - had no idea what ailed their aged leader and left him clinging to life in a ward at the Ulster Hospital in Dundonald.
It was only through a chance remark during a dinner in London with one of the 'Doc's' longest-standing friends that they found out what nearly claimed the life of one of Ireland's most belligerent politicians.
Even today Robinson and Dodds have never openly divulged what was said at that dinner about Ian Paisley's grave condition.
The Paisley family has never told them, which perhaps wasn't surprising given the antipathy between Ian Paisley Jnr and the man who succeeded his father as the DUP leader and First Minister.
While Robinson would acknowledge the ability of 'Junior', as he is referred to throughout the DUP, at organising elections in North Antrim and his earnest constituency work, no warmth exists between the son of the former leader and the new leader.
Ian Jnr suspected Robinson of briefing against his father during that almost-terminal illness in 2004 when, in reality, Robinson merely told those who asked - and everyone did - that the Doc was very ill and he didn't know what was wrong with him, which was the truth until that dinner in London when the diagnosis spilled out.
Later it emerged that Paisley was so gravely ill that the Free Presbyterian Church-organised prayer vigils to request divine intervention.
Ultimately, it was a change in his medication that saved Ian Paisley's life and reversed an accumulation of life-threatening side-effects that one long-term medication had inflicted upon his ageing system.
On his recovery, in September of 2004, he did concede in his column in The Revivalist - the Free Presbyterian magazine - that he had walked "along death's shadow".
In spite of this public admission, Ian Paisley characteristically reverted to his notorious bombastic style to admonish journalists for elevating the gravity of his illness to the critical level that it had actually reached.
We don't get that knockabout stuff today from the DUP, because Peter Robinson and other senior figures in the party feel that it doesn't suit a modern image.
Anyway Peter doesn't 'do' public humour comfortably, although privately, providing confidence is assured, he will spin some of the tittle-tattle that circulates in all political parties.
Generally, though, he and his lieutenants - his son in particular - patrol the ranks to discourage unapproved disclosures that could harm the party's strategy.
In a way the DUP is a mirror of Sinn Fein without the military wing: lines are provided to the media on a controlled basis by those approved to leak and only the most senior DUP MPs, or a few long-standing party figures, are prepared to utter off-the-record insights that illustrate internal dissatisfaction or personal analysis.
The heyday of the 'Doc' and his 'Chuckle Brothers' era are long gone and the Free Presbyterian Church's bloc support for the party is no longer assured.
Which is why, in the current fevered row over the devolving of policing and justice powers, little will be said of which Peter and his lieutenants do not approve.