Speaking abstractly, this universe consists of matter and space, and practically all the issues we can deal with are understood through the interaction of electrons and photons, whose states and motions are described by quantum electrodynamics. The importance of Heisenberg’s uncertainty principle and Pauli exclusion principle should be particularly emphasized. When considering more specific issues on metallic materials, the properties of materials are usually subject to their crystal structures and microstructures, and the structures are determined by the bonding among atoms. To discuss properties of materials, spatial rearrangements of constituent atoms, the changes in chemical bonding of atoms, and the stability of the bonds, i.e., reactions are essentially important. Therefore, the understanding of various issues in materials should follow the logical chain of bonding-structure–property-reaction is important. The basis of this logical framework is established on Democritus’ idea of atomism that matter needs vacant space in motion. In the world described by quantum electrodynamics, the stability and reactivity of materials depends on how the electron configuration departs from the one of inert gas atom. In this chapter, we summarized the above description as two definitions, ten axioms and ten theorems and presented as the manifest of the fundamental principles we trust.