 As we have seen in this case, even very fruitful applications of physical and chemical theory at the microscopic level are often insufficient to reduce chemically important properties. Whether the general notion of chemical substance, or the property of being a particular substance for each of the millions of known substances, can be reduced to microstructure needs to be demonstrated and not merely assumed. While there is no in-principle argument that reductions will always be impossible, essential reference is made back to some macroscopically observable chemical property in every formal attempt of reduction that we are aware of. In the absence of definite arguments to the contrary, it seems reasonable to suppose that chemistry employs both macroscopic and microscopic concepts in detailed theories which it strives to integrate into a unified view. Although plenty of chemistry is conducted at the microscopic level alone, macroscopic chemical properties continue to play important experimental and theoretical roles throughout chemistry.