Four Classical Elements. Classical elements typically refer to the concepts of earth, water, air, fire, and aether, which were proposed to explain the nature and complexity of all matter in terms of simpler substances. Ancient cultures in Persia, Greece, Babylonia, Japan, Tibet, and India had similar lists, sometimes referring in local languages to air as wind and the fifth element as void. The Chinese Wu Xing system lists Wood, Fire, Earth, Metal, and Water, though these are described more as energies or transitions rather than as types of material. These different cultures and even individual philosophers had widely varying explanations concerning their attributes and how they related to observable phenomena as well as cosmology. Sometimes these theories overlapped with mythology and were personified in deities. Some of these interpretations included atomism, but other interpretations considered the elements to be divisible into infinitely small pieces without changing their nature. While the classification of the material world in ancient Indian, Hellenistic Egypt, and ancient Greece into Air, Earth, Fire and Water was more philosophical, during the Islamic Golden Age medieval middle eastern scientists used practical, experimental observation to classify materials. In Europe, the Ancient Greek system of Aristotle evolved slightly into the medieval system, which for the first time in Europe became subject to experimental verification in the 1600s, during the Scientific Revolution. Modern science does not support the classical elements as the material basis of the physical world. Atomic theory classifies atoms into more than a hundred chemical elements such as oxygen, iron, and mercury. These elements form chemical compounds and mixtures, and under different temperatures and pressures, these substances can adopt different states of matter. The most commonly observed states of solid, liquid, gas, and plasma share many attributes with the classical elements of earth, water, air, and fire, respectively, but these states are due to similar behavior of different types of atoms at similar energy levels, and not due to containing a certain type of atom or a certain type of substance. The Persian philosopher Zarathustra, aka Zoroaster, described the four elements of earth, water, air and fire as sacred, i.e., essential for the survival of all living beings and therefore should be venerated and kept free from any contamination. In Western thought, the four elements earth, water, air, and fire as proposed by Empedocles frequently occur; Aristotle added a fifth element, aether; it has been called akasha in India and quintessence in Europe. The concept of the five elements formed a basis of analysis in both Hinduism and Buddhism. In Hinduism, particularly in an esoteric context, the four states-of-matter describe matter, and a fifth element describes that which was beyond the material world. Similar lists existed in ancient China, Korea and Japan. In Buddhism the four great elements, to which two others are sometimes added, are not viewed as substances, but as categories of sensory experience. In other Babylonian texts these phenomena are considered independent of their association with deities, though they are not treated as the component elements of the universe, as later in Empedocles. They further suggest that all of creation, including the human body, is made up of these five essential elements and that upon death, the human body dissolves into these five elements of nature, thereby balancing the cycle of nature. The five elements are associated with the five senses, and act as the gross medium for the experience of sensations. The basest element, earth, created using all the other elements, can be perceived by all five senses, hearing, touch, sight, taste, and smell. The next higher element, water, has no odor but can be heard, felt, seen and tasted. Next comes fire, which can be heard, felt and seen. Air can be heard and felt. Akasha is beyond the senses of smell, taste, sight, and touch; it being accessible to the sense of hearing alone.