on, as it comes into contact with them. Air (breath)
also is regarded as food, passing through the arteries
from the heart, while the blood passes through the
veins from the liver. But the function of blood is
not understood ; blood is, like milk, "what is left
over" (πλεονασμόσ2) when nourishment has taken
place. Neither is the function of the heart understood,
and its relation to the lungs is never
The aspect of nutrition which appeals most to the
writer is the combination of unity and multiplicity
which it exhibits. Food is one ; yet it has the
power of becoming many things. Similarly the
animal organism is one, with many parts vitally
connected with the whole, so that they act in
complete sympathy with it and with one another.
Food, says the writer, has "power" (δύναμις2), and
so has the body. This "power" seems to be the sum
total of its properties, although these are not yet
regarded as abstractions. It is one and many ; one
in its essence, many in its manifestations. But
"power" in its various forms is manifested only in
relationship to other things ; it is not independent,
being latent until called into action by a suitable
environment. In modern language, the author feels
that qualities are relations. Wine is good (or bad)
in certain circumstances ; so is milk and all other
foods. All things are good or bad πρός2 τι (Chapters
XIX and XLIV).
This theory of δύναμις2 with its insistence upon
relativity helps in assigning a date to the document.
A similar account of δύναμις2 is given in Ancient
Medicine, the date of which is approximately 420 B.C.
The theory of relativity, implied in the doctrine of