About Avicenna: Avicenna is regarded as one of the most significant thinkers and writers of the Islamic Golden Age. Of the 450 works he is known to have written, around 240 have survived, including 150 on philosophy and 40 on medicine.
Therefore in medicine we ought to know the causes of sickness and health.
The knowledge of anything, since all things have causes, is not acquired or complete unless it is known by its causes.
Now it is established in the sciences that no knowledge is acquired save through the study of its causes and beginnings, if it has had causes and beginnings; nor completed except by knowledge of its accidents and accompanying essentials.
The world is divided into men who have wit and no religion and men who have religion and no wit.
That whose existence is necessary must necessarily be one essence.
As to the mental essence, we find it in infants devoid of every mental form.
