It is argued that purposive action of living things plays a crucial role in Darwinian evolution. As evolution proceeds, the mechanisms of evolution evolve as well, giving an increasingly important role to purposive action - to be understood in a sense which is compatible with physics (the atom of purposiveness being the thermostat). Nine versions of Darwinian theory are distinguished. The first denies that purposive action has any role in evolution at all; each successive version gives an inceasingly important role (...) to purposive action. Of fundamental importance is The Principle of Non-Circularity: The theory must not presuppose what it seeks to explain. (shrink)