 At the basis of this view was Grosseteste’s view that natural agents act by the multiplication of their power or species, a view Roger Bacon was to develop in detail.  Grosseteste was, of course, thinking of the action of light. He holds that knowledge propter quid must be through angles, lines and figures because a “natural agent multiplies its power from itself to what it acts upon, whether it act upon the senses or upon matter” (Baur 1912, 60).  Grosseteste holds that the intensity of operation of the natural agent will be a matter of its distance from what it acts upon, the angle at which it strikes it, and the figure in which it multiplies its operation, this being either a sphere or cone. He establishes certain rudimentary rules to this effect, such as that the shorter the distance, the stronger the operation. 