Answer:
Illness occur due to unbalance of these four substances of body.
Explanation:
The theory of the four humors greatly explained the Hippocrates and Galen methods of treatments and preventing illnesses because the theory of the four humors helps in the treatments and preventing illnesses. According to this theory, blood, yellow bile, black bile, and phlegm are the four substances from which our body is formed so if these four substances works properly our body is normal whereas if any defect or unbalanced occurs in one of them, it leads to illness.