Although the poor lack the self-restraint of the rich and wealthy to reproduce beyond the population that the food supply is able to support, the population must be governed in order to supply the demands of the rest of the population, through both preventative and positive population checks. The principle reason that the population must be kept in check is because an unchecked population increases exponentially, while the food supply and substance only increase linearly. Through both preventative and positive population checks, the population growth curve must be kept below the growth curve of the vital resources; otherwise there is not enough resources and food per person. Malthus suggests that parents should consider the financial stability of their family if they wish to have a child, and not succumb to the primitive instincts of man. Malthus furthers his argument to include that it is the needy and underprivileged people's fault that they are at the bottom of society, and they should not spread their wealth too thin by having multiple children, but instead, focus on their own ascent up the social ladder, and strive towards increased financial stability. Malthus theorizes that it is the fault of the poverty-stricken that they remain poor, and if they are able to overcome the natural instincts of man, they will climb up in rank on the social ladder, and escape the bonds of poverty.