"I have this phobia," he admits," about having my body penetrated surgically."
Observing Willem Dafoe approaching the base of Law's spine with a gigantic hole-punch, the audience cannot help but share his anxiety. The frisson that results - a beguiling hybrid of fascination and repulsion - is the archetypal Cronenberg effect.
The Canadian writer-director has been patrolling the border country between arousal and nausea for more than 30 years now (his hour-long debut, Stereo, was first screened in his homeland in 1969). The single-mindedness with which he has done this is the subject of much speculation.
Some call him a prophet. Cronenberg's films certainly seem to anticipate many of the most unforeseeable developments in modern life - from the Aids virus in Shivers and Rabid, to Noel's House Party in Videodrome and the career of Eileen Drewery in Scanners. However, the director himself has "too much respect for the element of the unknown" to believe prophecy to be either possible or worthwhile.
Biographical determinists bring up the early death of his father from a horrible wasting disease that meant his bones lost the ability to process calcium. Cronenberg admits to the inevitably dramatic impact of that event, but points out that his film career was already well under way by the time it happened.
"In terms of portrait of the artist, forget it," he says firmly. "I was born knowing this stuff."
In person, David Cronenberg is a cerebral but far from geeky presence. Now 56 years old, the man who once observed: "Decay might as well be what you want, because it's what you're going to get" shows no outward sign of physical deterioration. In fact he looks downright chipper. Perhaps he is enjoying the contrast with his last promotional visit to Britain, when the Daily Mail was camped on his doorstep, proclaiming Crash to be the end of civilisation. This time round, things are looking much more propitious.
You might say eXistenZ was the David Cronenberg film for people who don't normally like David Cronenberg films, if that didn't risk alienating his fan base, who will undoubtedly love it too. Either way, it feels like the most complete piece of entertainment he has ever made. Did he know when he was making it how appealing it was going to be?
"I knew it was maybe a little more accessible than some of my other movies, but the film I started to write was not the one I ended up making."
Early drafts of eXistenZ's script did not, in fact, contain the game that ended up supplying the main body of the film. The original plan - which was inspired by a conversation with Salman Rushdie - was to focus on the central conceit of a female game-designer being pursued, using the game itself as "an elegant tease" and concentrating on "how an artist on the run dealt with being condemned to death".
What changed his mind?
"By page two I was desperate to find out what the game was, and I thought: 'If I feel that way, the audience will. How can I deny them?'"
This spirit of enquiry, of wanting to show things that would otherwise remain unseen, has always been fundamental to Cronenberg's idea of film- making, from the vertical slit that opened up in James Woods's stomach in Videodrome to Jeremy Irons's selection of gynaecological instruments in Dead Ringers.
"If I think of this amazing animal that seems to exist for playing games," Cronenberg enthuses, "I'm very interested immediately in how it works - what musculature does it have? What is the size, the colour, the texture of it? Does it move? Does it make sounds?"
As befits a man more interested in building things than in taking them apart, Cronenberg proclaims himself "not a big fan" of what he calls "the deconstructional approach to film - whether that be Scream or Shakespeare in Love". Yet in eXistenZ, his familiar blurring of the line between flesh and machine is combined with a - for him - uniquely playful attitude to narrative form. Arguably the film's most impressive achievement is the way it builds up games within games without ever losing its narrative grip.
In fact, the scenes in eXistenZ where Jennifer Jason Leigh fears for the safety of her gamepod creation are some of the most emotionally affecting Cronenberg has ever filmed. The touching parental love she exhibits towards her artistic creation suggests a personal echo in the director's own experiences.
Although the bulk of the screenplay was written before Crash came out, the film carries the clear imprint of Cronenberg's own small-scale version of the Rushdie affair.
"The Satanic Verses was Imax," Cronenberg smiles wanly, "and Crash was Super-8. My life was not threatened, but I can still understand the hopelessness of Rushdie trying to explain to the Ayatollah that he was not being literal: that these were characters... I have children, and a movie is not exactly like a child, but the pain you feel at the thought of your movie being cut - let's say chopped - by censors, is very real.
"They are responding to an idea of the film which is often created by people who haven't seen it, but even though they're essentially trying to destroy their own version of your film, it's your version that actually gets killed. What you have in situations such as this is a clash of incompatible realities. On one level, it's a very abstract thing, but at some point - in Rushdie's case when people start trying to kill you - that abstract becomes physical."
In dramatising the point at which the abstract becomes physical (and vice versa), eXistenZ builds its house of games on philosophical foundations that Jean Paul Sartre would have approved of.
In a moment of great animation, Cronenberg describes the thrill of film- making as "like being involved in the evolution of a new species".
The Islamic fundamentalist perspective on this would presumably be that this is the writer-director playing god.
"Yes, but my answer to that would be that God is a human creation. So the fundamentalists and I are doing the same thing. I'm just being a little more direct."
'eXistenZ' opens on 30 April