Unlike the photography and prints, I never catalogued, kept track of or exhibited the sketches. I sold some occasionally, but never saw myself as a graphic artist. They became more important to me thanks to the exhibition, however, and I realized that these drawings were quite interesting after all.

The truth... When they have a similar structure to and are organized in as truthful a way as nature. When I look out of the window, then truth for me is the way nature shows itself in its various tones, colours and proportions. That's a truth and has its own correctness. This little slice of nature, and in fact any given piece of nature, represents to me an ongoing challenge, and is a model for my paintings.

Almost every work of art is an analogy. When I make a representation of something, this too is an analogy to what exists; I make an effort to get a grip on the thing by depicting it. I prefer to steer clear of anything aesthetic, so as not to set obstacles in my own way and not to have the problem of people saying: 'Ah, yes, that's how he sees the world, that's his interpretation.'

Throwaway snapshots come closest to achieving the state of pure picture.

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.

I wanted to say something different: the pictures are also a leave-taking, in several respects. Factually: these specific persons are dead; as a general statement, death is leave-taking. And then ideologically: a leave-taking from a specific doctrine of salvation and, beyond that, from the illusion that unacceptable circumstances of life can be changed by this conventional expedient of violent struggle.

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.