The fundamental constituents or elements (stoicheia) of physical bodies are—theoretically—earth, air, fire and water. However, it is also legitimate to state that the elements are the hot, the cold, the wet and the dry; and indeed it is this latter model which is of the greatest explanatory value for Galen, and which he employs almost universally in his accounts of bodies and their physical change (for example in Temp., and more generally in his work on health, disease and pharmacology). He tends to present the difference between the two forms of analysis as philosophically unimportant: it is just a question of whether one prefers to talk in terms of qualities (poiotētes, i.e., the hot, etc.) or of bodies (sōmata, i.e., fire, etc.). However, the formulation in terms of the cosmic elements (fire, earth, air, water) is important for Galen, because it is central to his argument that the only coherent way in which a theory of elements in the body can be understood is in terms of the extremes of qualities; and, further, that (since, e.g., the extreme of hot is fire) such an understanding automatically entails the equivalence of those elements in the body with the elements outside the body, in the cosmos: fire, earth, air and water.