Following Socrates' advice "You should learn all you can from those who know. Everyone should watch himself throughout his life, and notice what sort of meat and drink and what form of exercise suit his constitution, and he should regulate them in order to enjoy good health." Based on biological, chemical and physical considerations I have attempted to synthesize guide lines for an optimal diet from the vast literature. For an offshoot of the primate line it may be wise not to stray too far from the line's surprisingly uniform predominantly frugi- and herbi-vorous diet that is only lightly supplemented by hunted small mammals, eggs, nuts, insects, etc. By dry weight raw wild fruit contains fats, proteins, carbohydrates, digested and undigested fiber in the approximate proportions 5 : 7 : 14 : 17 : 17. The fat component contains both essential fatty acids, about 23% linoleic and 16% alpha-linolenic, the latter severely lacking in Western diets. The practical problem is how to as best as possible, but not religiously, approximate this diet with super-market items.