The second epistemological axiom is about the vital importance of knowing, teaching and learning the concept of the chemical bond. If it is the central paradigm of chemistry, it is not only important; it is inevitable. The chemical bond, with its orbitals, electrostatic potential, electron density, and energy patterns, provides the ABC of chemistry work, research, and education, and nothing can be built without it. Therefore, no chemist is a real chemist without understanding the chemical bond.