 Before assembling the ingredients of these first two chapters, Darwin then introduced in chapter three the concept of a “struggle for existence”. This concept is introduced in a “large and metaphorical sense” that included different levels of organic interactions, from direct struggle for food and space to the struggle for life of a plant in a desert. Although described as an application of Thomas Malthus’s parameter of geometrical increase of population in relation to the arithmetical increase of food supply, Darwin’s use of this concept in fact reinterprets Malthus’s principle, which was formulated only with reference to human population in relation to food supply. It now becomes a general principle governing all of organic life. Thus the organisms comprising food itself would also be included. Through this universalization, the controls on population becomes only in the extreme case grounded directly on the traditional Malthusian limitations of food and space. Normal controls are instead exerted through a complex network of relationships of species acting one on another in predator-prey, parasite-host, and food-web relations. This profound revision of Malthus’s arguments rendered Darwin’s theory deeply “ecological” as this term would later be employed. The abundance of red clover in England Darwin sees as dependent on the numbers of  pollinating humble bees  which are controlled by mice, and these are controlled by the number of cats, making cats the determinants of clover abundance. The abundance of Scotch Firs is limited by the number of cattle, to cite two examples employed by Darwin (Origin 1859: 72–74). This recognition of complex species-species interactions as the primary means of population control also prevents one from reading the Origin as a simple extension of British political economy and the competition embedded in Victorian industrialization to the natural world.