ABSTRACT
If science is to be possible men must possess certain essential powers. Among these is the power of affecting the sequences of states and events in the world in the sense of bringing about effects which but for their action would not have been realized. In this way men contribute to the universal maelstrom of existence. More specific to men is their power to initiate and prevent change in a purposeful way. The possession of this power seems to stem from the fact that men are material things with a particular degree of neuro-physiological complexity which enables them to monitor and control their own actions. Foremost among the powers necessary for science and, as far as we know, distinctive of men is their power of intentional action, which enables them to act self-consciously on the world: that is not just to monitor and control their performance, but to monitor the monitoring of their performance: to plan, to act and so to make an anticipatory commentary come true.
