Model Cities

'And yet I have constructed in my mind a model city from
which all possible cities can be deduced,' Kublai said. 'It contains
everything corresponding to the norm. Since the cities that
exist diverge in varying degree from the norm, I need only
foresee the exceptions to the norm and calculate the most
probable combinations.'

'I have also thought of a model city from which I deduce all
the others,' Marco answered. 'It is a city made only of
exceptions, exclusions, incongruities, contradictions. If such a
city is the most improbable, by reducing the number of elements,
we increase the probability that the city really exists. So I have
only to subtract exceptions from my model, and in whatever
direction I proceed, I will arrive at one of the cities which,
always as an exception, exist. But I cannot force my operation
beyond a certain limit: I would achieve cities too probable to
be real.'

From Invisible Cities, Italo Calvino. 1974