Symmetry is the origin of all interactions
In Phil Anderson's review of Lucifer's Legacy: The Meaning of Asymmetry by Frank Close, Anderson makes the following profound and cryptic comment. In a book focusing, as this does, on symmetry, it seems misleading not to explain the fundamental principle that all interaction follows from symmetry: the gauge principle of London and Weyl, modelled on and foreshadowed by Einstein's derivation of gravity from general relativity (Einstein seems to be at the root of everything). The beautiful idea that every continuous symmetry implies a conservation law, and an accompanying interaction between the conserved charges, determines the structure of all of the interactions of physics. It is not appropriate to try to approach advanced topics such as electroweak unification and supersymmetry without this foundation block. To see how this plays out in electrodynamics see here.