The third of the four headings into which Theoretical Medicine is
divided deals with the theory of Causes or Aetiology.
Now, the Causes are six. The first of these is Air. Air is essential to
keep the soul evenly balanced. For
as long as air remains pure, no debility Folio 8 is mixed in it and no foul wind. It is an unrecognised protection.

Every season produces diseases compatible with it and expels what is
incompatible. Thus, summer breeds bile and causes bilious diseases, but
cures cold diseases. And the like can be said of the other seasons.
Cold air is strengthening and improves the digestion. Hot air does just the reverse. A change in the Air is a cause of Pestilence. And if God will, See folio 141 that will be described later.
The second Cause is Food & Drink. When hot, these produce heat in the
body. And vice versa.
The third Cause is Bodily Movement & Rest. Movement breeds warmth
in the body. And vice versa.
The fourth Cause is Emotional Movement & Rest, as occurs in cases of
anger, joy, apprehension, grief, and modesty. These states set the soul
in motion, internally indeed but apparent externally. I will revert to See folio 24 these later if God wills.
The fifth Cause is Waking & Sleeping. Sleep causes the soul to bubble
within the body, although it cools the outside. Hence the sleeper requires some outer garment. Wakefulness is just the reverse of this.
The sixth Cause is Excretion & Retention. A balance between these
protects health.
The fourth of the four headings into which Theoretical Medicine is
divided deals with the Theory of Signs.
Black hair and a black body are signs of heat: the opposite a sign of cold.
Similarly, a fat body or a thin body. An excess of flesh is a sign of heat
combined with damp. Excess of fat is a sign of cold combined with damp. In the same way excessive desire for sleep is a sign of damp, whereas a Folio 9 diminished desire is a sigh of a
balanced temperament. Similarly the appearance of the organs is a sign. Capacious organs are a
sign of heat and the opposite a sign of coldness. In the same way dreams
show temperaments. The seeing of colours, yellow or red, or flashes of
light, all these are signs of heat. And their opposites are signs of coldness
Again, excess of body odour is a sign of heat: lack of it a sign of cold