Astrology and Supernatural Forces
Medicine was not scientific at this time. Oftentimes astrology and the supernatural arts were relied upon to determine the causative elements and treatment of a disease. Treatments and the gathering of drugs were based upon celestial geography. The astrological positions of the planets were also believed to cause threats or benefits to health. Saturn influenced longevity, the conjunction of Mars and Saturn were believed to have caused the plagues that hit England, and Mars was believed to cause tertian fever.
Supernatural arts such as sorcery, magic, and demonology were also the basis behind some medical concerns. Diseases believed to be caused by devils, spirits, demons, gods, etc. were to be challenged by charms, white magic, prayers and other such means. 
Elizabethan Medical Beliefs
The three main organs in the body according to Elizabethans were the heart, liver, and brain The liver was considered the great blood-forming nutrition-giving organ from which the four humours and natural spirits arose. The liver was also considered the origin of the veins which spread throughout every part of the body. The circulation of blood through these veins was a separate and closed system. The blood flow was considered to be in a static state versus that of a continuously current propelled by what we now know today as the heart. Elizabethans believed the heart to be the centre and seat of life. The arterial system accompanied the heart and transported vital spirits throughout the body. Again the circulation of blood throughout this system was not as we perceive it today but more of an agitated motion. The vital spirits in the arterial system were supposed to be like the nervous system of today. The heart was the seat of affections and emotions - joy, anger, hope, fear etc.- and the source of the soul's uneasiness. The brain was the seat of reason, memory, and imagination. This was the centre of the rational soul with the spirits as its instruments 
The theory of humours
The theory of humours is based on the four elemental body fluids. The amounts of blood, yellow bile, phlegm, and black bile determined a person's physical or mental health. The logic behind the presence of these fluids was that each fluid gave off vapours that ascend to the brain and the person's temperament was decided by the state of his humours. The perfect temperament was one in which none of the humours dominated. A person with a dominant presence of blood was supposedly happy and generous. A dominance of yellow bile meant that the person was violent and vengeful. If a person were dull, pale, and cowardly it was presumed to be due to an excess of phlegm. Black bile justified someone's gluttony, laziness, or sentiment. 

Four qualities, four elements, four seasons, four humours
Based on a diagram from Isidoe of Seville, Liber de responsione mundi (Augsburg, 1472):
season	element 	humour	body fluid 	location 	
Spring	air	sanguine	blood	heart	
Summer	fire	choleric	"yellow bile"	liver	
Autumn	water	phlegmatic	phlegm	(various)	
Winter	earth	melancholic	"black bile"	spleen	
The humours each had associated physical and mental characteristics; the result was a system that was quite subtle in its capacity for describing types of personality.
Humour	Qualities	Element	Personality	
Sanguine	hot, moist	air	Optimistic, red-cheeked, corpulent, irresponsible (compare Falstaff).	
Choleric	hot, dry	fire	Short-tempered, red-haired, thin, ambitious (compare Hotspur).	
Phlegmatic	cold, moist	water	Sluggish, pallid, corpulent, lazy 	
Melancholic	cold, dry	earth	Introspective, sallow, thin (compare Richard II, Hamlet).	
In addition, different humours could be combined for more complex personality types: choleric-sanguine, phlegmatic-melancholic, and so on. 
Shakespeare and Medicine in the Elizabethan Era
William Shakespeare has been credited as being ahead of his time with regard to his understanding of the medical field. Critics exclaim that the proof of excellence lies within his dramas. Shakespeare has been displaced from his Renaissance environment by such critics. Shakespeare's era was a time of exploration in both the liberal arts and sciences. Many of his contemporaries also made use of medical references within their works. Shakespeare and his contemporaries took pride in the "turning over of authorities" in their work. By doing this, they would often times include accepted doctrines from the "authorities" such as Plato, Aristotle, Hippocrates <hippocrates.htm>, etc. in their work 
Correspondences
	Within hierarchies there were "correspondences": created beings whose status within the hierarchy were equivalent one to the other. Consider, for example, those at the head of each category: 		
	The angels	God	
	The universe	Sun	
	Society	King	
	The family	Husband	
	The human body	The head	
	Animals	Lion	
	Plants	Oak	
	Minerals	Gold	
	The list of such correspondences could be extended almost indefinitely. 		
Steps, ladder, chain, scale
The story of the creation could be seen as a logical progression from light, to the waters, to the earth, to planets, to animals, and finally to humans. In this image there is an orderly progression upwards. This sense of order, and its consequent fixed hierarchy, were convenient for the stability of both church and state. 
Primary qualities and the spheres
From the time of the ancient Greeks, philosophers had been fascinated by the basic question of the nature of matter. Empedocles suggested that all matter was made up of four basic "roots" or elements (earth, air, fire, and water) and two basic forces, harmony and discord. Later writers, including Aristotle, argued that the four elements themselves expressed combinations of more basic qualities: hot, cold, dry, and moist. 
The planets shared the same four primary qualities as all created matter: hot, cold, dry, moist. Thus in the illustration of the spheres, each planet has its combination; the problem of dealing with seven known planets and only four qualities was solved thus: 
Saturn	cold and dry	
Jupiter	hot and moist	
Mars	hot and dry (extreme)	
The Sun	hot and dry (moderate)	
Venus	cold and moist (extreme)	
Mercury	hot with hot, cold with cold, etc.	
The Moon	cold and moist (moderate)	
Gendered planets
A further neat division was made between the male and the female. The male's natural temperament was hot and dry (Mars, warlike, in extreme; the sun, in moderation); the female was cold and moist (Venus or the moon)

In addition to the sprites and fairies that appear in some of the early comedies (Puck in A Midsummer Night's Dream) and in the later romances (Ariel in The Tempest), Shakespeare includes both ghosts and witches in his tragedies. Although the spirits of Shakespeare's imaginative fairy realms are only real within their domains, and while the ghosts who appear to Richard III and Macbeth are guilty-ridden hallucinations, the ghost of Hamlet and the witches or weird sisters of Macbeth are given substance. Belief in ghosts and in witches remained widespread in Elizabethan England: King James I, Elizabeth's successor and the patron of Shakespeare's dramatic company, wrote a tract on the nature and reality of witches. Shakespeare may not have believed in the supernatural, but he was certainly aware that such beliefs were held by many within English society (including, in the case of King James, those at its top). That being so, he used the supernatural as both a device to advance or embellish his plots and in a metaphorical sense.