If the head of Isis's internal security unit tasked with hunting spies for the infidels was himself a spy for the CIA or MI6, well, then, maybe.

If up to one quarter of Isis militants in a city such as Raqqa happened to be compromised as informers for one of the myriad branches of the Iraqi, Syrian or Kurdish security forces, perhaps there would be a chance.

And if governments in Baghdad, Damascus, London or Washington had secret strategic insight into the political thinking of Isis leaders - especially those willing to turn the movement away from "armed struggle" towards democratic politics - then, possibly, Jeremy Corbyn's call for a back channel to be set up between Isis and the UK would not sound so much like naive rubbish.

Alas, of course, Corbyn's proposal for a secret link between Isis's top commanders and agents from MI5 or MI6 is yet another example of the Labour leader's breathtaking ability to appear more and more ludicrous and disconnected from reality as each week passes.

It also demonstrates his profound misreading of the peace process and the state of the Provisional IRA as it entered the 1990s.

There is no penetration of Isis like the British State had vis-a-vis the IRA, other republican groups or, indeed, loyalists, during the Troubles. Nor is there any compromising faction emerging within Isis's ranks that believes violence has run its course and is now acting as a barrier to its political wing's progress.

For someone who has earned a reputation over the decades as an ideologue, it is striking that Corbyn's call for an Irish peace process solution to a radically different problem in the Middle East exposes a shocking lack of ideological understanding on the Labour leader's behalf.

Given his closeness to Sinn Fein during the conflict he should know that its ideology was (at least in name, but not so often in its deeds on the ground) rooted in secularism. While the IRA and its leaders would often exploit sectarianism and tribal fear, it claimed to be influenced by the secular ideology of the 18th century United Irishmen, a group that was coloured by the anti-clerical French Revolution of 1789.

Of course the founding fathers of 20th century republicanism, whom the modern Republic is lionising in this centenary year, included Patrick Pearse (below left), who sought to exploit Catholic notions of blood sacrifice on Easter Week to obtain mystical, near-theological justification for the 1916 Rising.

Yet those around Pearse inside Dublin's GPO, and outside it too, were a mixed band of idealists fired up by often contradictory ideological visions - from the crude Marxist-syndicalism of James Connolly to those who wanted an Irish monarchy established to replace the English one.

By total contrast, an organisation such as Isis represents a coherent, holistic, all-encompassing, maximalist vision of the world and, indeed, the after-life, that spares no time for complexity or diversity. There is no God but Allah and Mohammed is his Prophet.

Moreover, there is only one way in its Islam, and that is the Sunni tradition. All who do not accept its vision of the Muslim faith and fail to convert must either die or serve as slaves - sexual or otherwise in the case of captured women - to the true believers.

Even those who also believe in Allah and Mohammed from other traditions, but especially the Shia branch of Islam, in Isis's eyes are as much enemies of the one true way as Christians, Jews or, worse still, non-believers.

All of this is, quite literally, in a sense a world away from the ideology of Irish republicanism - even that branch of it which was really, as Conor Cruise O'Brien once described it, "good, old-fashioned Catholic nationalism dressed up in trendy gear".

At a superficial level there may be some parallels between that "good, old-fashioned Catholic nationalism" and extreme Islamism. There is the ubiquity of the death cult and the veneration of the armed martyr.

Some more naive observers of Irish republican/nationalist history point to the hunger strikes - from Terence McSweeney to Bobby Sands (left) - and draw a parallel with the suicide bomber and murderers of Hamas, al-Qaida and now Isis. Yet, it is in fact a wholly bogus comparison and one that displays confusion about the nature of tactics.

Over a decade ago I helped co-produce a documentary on the IRA bombing campaign for RTE. During one interview with a former IRA "engineering officer", who was responsible for blitzing Belfast in the 1980s, I asked him if anyone had ever volunteered for a suicide mission to blow themselves up at an Army checkpoint or a police station. He looked at me as if I had lost my sanity and said, quite emphatically, that if anyone had come forward offering to be a suicide bomber he would have stood them down from the organisation and sent them home (or, preferably, to the nearest psychiatrist).

So, what about the hunger strikers? Didn't they sacrifice their own lives for the cause? The IRA bomb strategist's answer was telling: with the hunger strike there was always until the bitter end at least a back door to life, a chance to call off the death fast and save themselves. There is no back door to life for the suicide bomber, especially one who is brainwashed and stupid enough to believe there are 72 virgins waiting for them after blowing themselves to pieces.

Unlike Islamism, Irish republican history is also punctuated by a series of compromises as purist militants come back to reality. So, a majority who followed the idealism of Pearse and Connolly ended up in 1921 siding with pragmatists such as Michael Collins and fighting a civil war to obtain what was essentially Home Rule for the 26 counties. Many of the diehards who violently opposed the 1921 Treaty eventually came to accept the dispensation, abandon armed struggle and formed Fianna Fail.

Some - but not all - of the guerrilla fighters of the 1956-62 border campaign, including Sean Garland, came around to compromise too and created the Official IRA.

Finally, the majority of Provisionals who accused old comrades such as Garland of treachery and "running away from the struggle" ended up in a partitionist Ulster parliament, accepting the 'unionist veto' and becoming merely persuaders for a United Ireland, because they too came to learn (eventually) that violence was not working.

Isis is hardly likely to split any time soon into those who want to keep on fighting and those who think they can bring about a caliphate in the Iraqi national parliament or a new post-Assad, all-party assembly in Damascus. There are no Michael Collins-style stepping stones towards Isis's ultimate goal - only one truth path littered with blood and gore.

Given the ideological and historical chasm between Isis-style medieval visions of Islam and Irish republicanism/nationalism, Jeremy Corbyn's call for a back channel is so absurd and ahistorical as to be meaningless.

Belfast Telegraph