CHAPTER X 

 MALTHUS 



THE theory of Hal thus has been the cause of a vast 

 amount of confused and unnecessary argument. Let us 

 take first the famous progressions. Mai thus assumed that 

 the potential rate of increase of the population is geomet- 

 rical, and that the rate of increase of the food supply 

 can only be arithmetrical. The potential rate of increase 

 of the population is undoubtedly geometrical, apart from 

 the principle outlined in the foregoing pages. Malthus 

 knew of no checks upon the birthrate except such as 

 are purely incidental. He knew nothing of a regulating 

 principle which causes deathrate and birthrate to rise 

 and fall together. We have seen that the potential 

 fertility of a married woman who lives a normal length 

 of life may be put at about thirty children at a moderate 

 estimate. This number has often been exceeded, while 

 among very fertile races twenty in a family is by no 

 means uncommon. 



Now, if this potential fertility were actually realised, 

 and if the children all lived a normal length of life, in 

 their turn realising to the full their potential fertility, 

 the result would be a devastating flood of humanity 

 which would sweep the earth from end to end like a 

 swarm of locusts. The potential geometrical rate of 

 increase, therefore, given a fully realised birthrate and 

 a nominal deathrate, is indisputable. 



But the necessarily arithmetrical ratio of increase of 



162 



