And then the work bears a strong sense of leave-taking for me personally. It ends the work I began in the 1960s (paintings from black-and-white photographs), with a compressed summation that precludes any possible continuation. And so it is a leave-taking from thoughts and feelings of my own on a very basic level. Not that this is a deliberate act, of course; it is a quasi-automatic sequence of disintegration and reformation which I can perceive, as always, only in retrospect.

All photographs are far more important than any painting.

Yes, we were amazed when that happened. It was a real joke to us. Konrad Lueg and I did a Happening, and we used the phrase just for the Happening, to have a catchy name for it; and then it immediately got taken up and brought into use. There's no defence against that - and really it's no bad thing.

It was not possible for us to produce the same optimism and the same kind of humour or irony. Actually, it was not irony. Lichtenstein is not ironic but he does have a special kind of humour. That's how I could describe it: humour and optimism. For Polke and me, everything was more fragmented. But how it was broken up is hard to describe.

Perhaps the Doors, Curtains, Surface Pictures, Panes of Glass, etc. are metaphors of despair, prompted by the dilemma that our sense of sight causes us to apprehend things, but at the same time restricts and partly precludes our apprehension of reality.

To me, grey is the welcome and only possible equivalent for indifference, noncommitment, absence of opinion, absence of shape. But grey, like formlessness and the rest, can be real only as an idea, and so all I can do is create a colour nuance that means grey but is not it. The painting is then a mixture of grey as a fiction and grey as a visible, designated area of colour.

I started doing 'figures', then, one day, all of a sudden, I started doing abstraction. And then I started doing both. But it was never really a conscious decision. It was simply a question of desire. In fact, I really prefer making figurative work, but the figure is difficult. So to work around the difficulty I take a break and paint abstractly. Which I really like, by the way, because it allows me to make beautiful paintings.