Table of Contents -- Introduction -- The tautological toolkit -- Rise and fall: The logistic equation -- Mechanics and gravity: Newton's dynamical equations and universal law of gravity -- The electromagnetic force: The Lorentz force law -- A local conservation law: The continuity equation -- Electrodynamics: The Maxwell equations -- Electromagnetic waves: The wave equations -- Solitary waves: The Korteweg-De Vries equation -- Thermodynamics: The three laws of thermodynamics -- Kinetic theory: The Boltzmann equation -- Hydrodynamics: The Navier-Stokes equations -- Special relativity: Relativistic kinematics -- General relativity: The Einstein equations -- Quantum mechanics: The Schrödinger equation -- The relativistic electron: The Dirac equation -- The strong force: Quantum chromodynamics -- Electro-weak interactions: The Glashow-Weinberg-Salam model -- String theory: The superstring action -- Back to the future: A final perspective.