Confusion on just what "fundamental" means I just read the Tao of Physics and I'm slightly confused. Are quarks and leptons fundamental units of matter or are they temporal manifestations of energy with E=mc^2? Is is that all matter is comprised of bundles of energy and that quarks and leptons are the most fundamental units created by this energy? What is the difference between matter particles and force carrier particles? Aren't they all just temporal manifestations of energy? And if so, why is Stephen Hawking so against books like the Tao of Physics that compare physics to Eastern mysticism? Also, if photons are massless, why is light affected by gravity in General Relativity?