In short, the science of human nutrition cannot be built on attractive theories and wish fulfilment fantasies; it must have its roots in observed facts, it must aim at finding out what sort and quality of food promotes the best kinds of men and women, both in mind and body. The food that makes the uncivilized Zulu or Masai a fearless but blood-thirsty fighter is not likely to be such as will make the Englishman cool-headed and intelligent.