In modern textbooks the nature of the cause of physical movement is usually defined as follows: 'Any change in the state of movement of a portion of matter is the result of the action on it of another portion of matter.' This represents a truth if it is taken to describe a certain kind of causation. In the axiomatic form in which it is given it is a fallacy. The kind of causation it describes is, indeed, the only one which has been taken into consideration by the scientific mind of man. We are wont to call it 'mechanical' causation. Obviously, man's onlooker-consciousness is unable to conceive of any other kind of causation. For this consciousness is by its very nature confined to the contemplation of spatially apparent entities which for this reason can be considered only as existing spatially side by side. For the one-eyed, colour-blind spectator, therefore, any change in the state of movement of a spatially confined entity could be attributed only to the action of another such entity outside itself. Such a world-outlook was bound to be a mechanistic one.