At the time of the Islamic conquests, philosophers and educated men had, by and large, accepted the Aristotelian view of the world. In this metaphysics, all of reality was composed of earth, wind, fire and water categorised into two broad categories of dry and hot, cold and wet. The heavier elements, earth and wind, gravitated to the centre of the universe whereas the lighter elements fire and air moved upwards and away from it. Surrounding the universe was the ether, a fifth element. The earth was considered to be at the centre of this universe. The elements had a hierarchy of importance with the earth considered the lowliest whilst the higher up you moved in the elemental chain the more worthy the element up until ether. Beyond that were the angels/demons/gods and so on, who were all subservient to The One if you were a neo-Platonist or "The Unmoved mover" if you were a strict Aristotelian. The earth was considered in the sub-lunar layer of this cosmology, the planets were beyond that and the outer limit were the stars, which rotated around the earth and possessed their own, higher, intellects and were closer in the hierarchy to this One and His influence. The fact that there was generation and corruption on the earth, as well as any movement at all, was due to the mixing and churning of these elements in the sub-lunar level. As a result, we and all other creation were a mix of these elements and conditions to varying extents. Where you were born and what stars were in the sky at the time influenced your character and fortune and these continued to exert an influence indirectly on you as a result of their effect on one or more of the elements within you.
The early Muslims largely accepted this view of the world and any educated man worth his salt was to have some grasp of these concepts. Revelation was concerned mainly with the conduct and morality of individuals and the nature of their relationship with their creator rather than reveal what some today call "scientific truth". Anyhow, the early Arab philosophers picked up on these strands of thought as the Greek texts began to be translated and the first Arabic philosopher al-Kindi pondered the nature of The One in his "On First Philosophy", only parts of which remain extant, before writing extensively on everything from the soul and the natural sciences to the making of swords and lenses. This understanding of the human body as a mixture of these four elements was the basis of medical knowledge and how physicians would deal with various symptoms in their patients. One method they used, which I had heard of before, was music. It was only I read a plaque in the Azm palace in Damascus on music that I understood the importance of it. The early Ouds had four sets of double strings, the fifth, middle one, being added by Zeryab in al Andalus during the period of Islamic rule.
Each of these four strings corresponded to one of the four elements and when plucked in different combinations and ways, were supposed to stir the necessary parts of the body or human emotion and had beneficial effects on them. The highest cord on the Oud, the zir, was yello and represented yellow bile. The second set of strings, the mathna, were red and associated with blood. The third set, the mathlath, were white and were related to phlegm whilst the fourth set, bam, were associated with the colour black and yellow but I do not know what they corresponded to in the human body.
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