is acknowledged that to raise new food requires greater labour and new inventions, while to bring new men into the world requires nothing more than in all times past, the disparity of the two is already admitted. The fact that the two processes are both dependent on the action of man, and both practically illimitable, does not prevent them from being essentially unlike.[128] Objectors often suppose that the tendency of population to outrun subsistence is contradicted by the existence of unpeopled or thinly-peopled countries, just as if the tendency of bodies to attract each other were contradicted by the incompressibility of matter. The important point to notice is that the one power is greater than the other. The one is to the other as the hare is to the tortoise in the fable. To make the slow tortoise win the race, we must send the hare to sleep.[129] Carey (_Social Science_, vol. i. ch. iii. § 5) represents the view of Malthus by the following propositions:—1. “Matter tends to take upon itself higher forms,” passing from inorganic to vegetable and animal life, and from these to man. 2. Matter tends to take on itself the vegetable and animal forms in an arithmetic ratio only. 3. It tends to take its highest form, man, in a geometrical ratio, so that the highest outstrips the lowest. In short he believes that Malthus holds the geometrical increase to be true of man alone, and only the arithmetical to be true of animals and vegetables. But Malthus really attributed the tendency to geometrical increase to all life whatsoever, and arithmetical to all food, as such. In Macvey Napier’s Supplement to the _Encyclopædia Britannica_ (1824) Malthus has left his mature statement of his cardinal principles, and, at the risk of repetition, that account may be added here. The main difference from the essay is in arrangement of the leading ideas; and we may learn at least what he conceived to be their relative importance towards the end of his life.