ABSTRACT
Policy networks are historical systems, whose state at any given time depends on their state in the past. Knowledge of a system’s earlier states, however, is insufficient to predict further development; the latter is underdetermined by the system’s earlier states. The ozone controversy of the 1970s influenced the ozone controversy of the 1980s, and the latter influenced the climate debate of the 1990s. No predictions can therefore be made; and so no attempt should be made, in reconstructing the historic data, to provide a teleological construction. Thus, in marked contrast to attempts to explain this case in a deterministic or reductionist way, my repeated reference to the contingencies of development.
