Because it contains the strongest and most influential among the others, it has become effective in the terrestrial realm. This is because the nature of this sphere is heat and dryness. Heat is stronger than cold, and dryness is stronger than moisture. Since this sphere contains the strongest of these four elements within itself, it has become effective (influential).
One of the levels of wujūd (existence) is also the sphere of air (kurrat al-hawāʾ). This is the sphere called the air sphere, whose nature is heat and moisture, and which is itself affected. Due to its moisture, it is influenced by the etheric sphere above it; due to its heat, it influences what is beneath it. The copy of this sphere in the human body is blood; the copy of the sphere above it is bile; and beneath it is found...