From this conception of the parallel evolution of earth and man light falls also on the historic event represented by van Helmont's discovery. Besides being a symptom of a revolution in man's way of experiencing the atmosphere, it speaks to us of some corresponding change in the spiritual-physical condition of the atmosphere itself. It was then that men not only came to think differently about air, but inhaled and exhaled an air that actually was different. To find out what kind of change this was, let us turn once more to man's own organism and see what it has to say concerning the condition under which matter is capable of being influenced by mechanical and magical causation respectively, in the sense already described.