It is in the nature of water ... to become transformed into earth through a predominating earthy virtue; ... it is in the nature of earth to become transformed into water through a predominating aqueous virtue.
AvicennaThe theory of medicine, therefore, presents what is useful in thought, but does not indicate how it is to be applied in practice-the mode of operation of these principles. The theory, when mastered, gives us a certain kind of knowledge. Thus we say, for example, there are three forms of fevers and nine constitutions. The practice of medicine is not the work which the physician carries out, but is that branch of medical knowledge which, when acquired, enables one to form an opinion upon which to base the proper plan of treatment.
AvicennaThe physical signs of measles are nearly the same as those of smallpox, but nausea and inflammation is more severe, though the pains in the back are less.
AvicennaPrayer is that which enables the soul to realize its divinity. Through prayer human beings worship absolute truth, and seek an eternal reward. Prayer is the foundation-stone of religion; and religion is the means by which the soul is purified of all that pollutes it. Prayer is the worship of the first cause of all things, the supreme ruler of all the world, the source of all strength. Prayer is the adoration of the one whose being is necessary.
Avicenna