Homo oeconomicus and homo politicus. Political economy, constitutional interest and ecological interest

Are modem democracies capable of preserving the constitution of liberty and capable of preserving the natural basis of human existence in the long-run? The achievement of these aims requires political actions toward fundamental changes in the life of modem societies. The respective political actors have to develop and to sustain long-term constitutional and ecological interests. Can these actors be conceived as homines oeconomici? Within public choice there have been important attempts to derive long-term interests on the basis of homo oeconomicus. These attempts have led, however, to theoretical difficulties. To develop a solution we introduce the notion of homo politicus. Homo politicus is concerned with the common search for the general interest of a political community which in traditional philosophy is called 'justice'. The concepts of homo oeconomicus and homo politicus are not mutually exclusive alternatives, but dimensions of human behaviour. Neither of them can be empirically observed in its pure form. We argue that we need a combination of both concepts to understand political phenomena. Thereby we seek to contribute to a theoretical basis which allows the derivation of the constitutional interest and the ecological interest.