At first sight his Democratic Unionist Party is an unchanging group of die-hards for whom politics is simply a way of fighting a religious war by other means, the party of straightforward anti-Catholicism and anti- Nationalism. But in fact it has undergone a sea change to become one of the most fascinating elements in the Belfast political equation and, potentially, one of the most crucial. Mr Paisley has led the opposition to the Good Friday accord, fighting last year's referendum campaign on an uncompromising "smash the Good Friday agreement" ticket.
In the assembly chamber, where his party holds 20 of the 108 seats, DUP members engage in hand-to-hand rhetoric, sometimes with Sinn Fein but most often with David Trimble's pro-agreement Ulster Unionists. Mr Paisley routinely attacks Mr Trimble's "treachery and betrayal".
Yet these assembly sessions can give a misleading impression of the underlying state of what is really going on politically, and of the health of the peace process. Unionism is certainly divided, as was shown in last week's vote when Unionist members voted 29 for and 29 against an important motion. But, with hardly an exception, unionist members adore the Stormont assembly. Unionist members of all factions are to be seen striding officiously through its marbled and gilded corridors, Hansards and sheaves of important- looking papers tucked under their arms.
Some of the more senior sweep ostentatiously through the corridors trailing aides, officials, press officers and bodyguards, a retinue designed to convey that they are people of influence and consequence. Many of the 108 members are, in other words, revelling in the trappings of power.
John Hume and the SDLP have been working towards something like this for many years, knowing in their bones that only an institution that could command cross-community support has any chance of taking root. This new Stormont is the natural result of their belief, held over the decades, that nationalist and Unionist must share power.
Sinn Fein came to the idea much later, having first had to swallow the concept of going into a building that, for decades, they had regarded as a symbol of Protestant supremacy and repression. Although they are among the least affected by the marble and the gilt, they still see it all as a valuable vehicle for pursuing their goals.
David Trimble's Unionists have settled in wonderfully, looking forward to the day when Westminster devolves real power to the new institution. The last quarter of a century has not been easy for Unionists as they have watched power slip away from their tradition, seen influence gained by John Hume and Gerry Adams and watched with trepidation the rise of Anglo-Irishry.
For them the assembly offers a chance to get a Unionist handle on things, an opportunity to get back into the game, an opening to regain some control of their own destiny. While it is not the ideal system for them, it nonetheless offers them access to the levers of power.
And the DUP, which fought so hard against all this, will also get a share of that power, for the arithmetical formula for doling out executive seats dictates that the party will have two places on the executive. Mr Paisley may be against the whole thing in principle, but in practice he will certainly take those seats.
The old warhorse is, in other words, preparing for government. In the meantime it is obvious that his men are among those who love Stormont most, who have the highest spring in their step as they pass proudly through its portals. They most love its grandiose charms, and they least want to lose it. "They treat this place like a country club," said one opponent.
Some will accuse the old man of hypocrisy in all this; others will figure that he has little choice but to go along with the new realpolitik imposed by the Good Friday agreement, a document whose craft and subtlety is gradually being revealed.
The Paisleyite desire to stay in the assembly and to get into government is going to be of crucial political importance, for it shows the difference between appearance and reality. However things may seem on the surface, David Trimble is not struggling to preserve the assembly from Paisley's attempts to destroy it; rather, both want to keep it going.
Furthermore, both unionist leaders probably believe that at some stage in the next few months the issue of arms decommissioning will be resolved one way or another, and that Sinn Fein will then take its seats in the executive. This will not deter Mr Paisley from taking his seats; he put up a great fight against the whole thing, but now he is prepared to lie back and think of Ulster.
Paisleyism has always reflected a schizophrenia within Unionism. At one level it is authoritarian and unforgiving of dissidents, as seen in its emphasis on law and order and maximum punishment for those who break the rules. On another level it embodies the politics of dissent, as is demonstrated by all those Paisleyite protests over the years.
Although these two instincts have often collided, the new executive will provide a cabinet that his men can simultaneously join and denounce. This may well be something close to Paisleyite heaven.
Last year's referendum on the Good Friday agreement recorded a 71 per cent endorsement of the accord, which meant that just over half of the Unionists approved of it. Although some have since argued that some Unionist support has ebbed away, it is in fact more likely that tacit acceptance of the agreement has increased.
At the political level, this is partly because the lure of office and status is so strong; at grass-roots level it is largely due to the time- honoured Presbyterian instinct to accept the will of the majority.
But there is also something deeper going on here. Whatever temptations were on offer, Paisley and his people would not be in such a participatory mood if they really believed that this agreement was trundling them inexorably towards a united Ireland.
There are many things he and his supporters would want to see changed in the Good Friday agreement; their attempts to alter it will probably form much of the stuff of politics in the years ahead. The bottom line, though, is that they do not fear the accord and are not in the business of wrecking it. The net effect is a strong Protestant consensus that the assembly should survive.
None of this means that the decommissioning deadlock will easily be resolved, and none of it provides a cast-iron guarantee that the peace process will remain on track. But it does mean that, despite all past setbacks and future hurdles, there are powerful and not always obvious factors that mean that survival is much more likely than collapse. Welcome to the peace process, Mr Paisley.