A systematic defense of the wave nature of light proposing that every point on a wavefront acts as a source of secondary spherical waves, a principle used to derive and explain reflection and refraction (including Snell’s law) and to account for phenomena such as double refraction and polarization in crystals; the work develops a geometric wavefront construction and invokes an elastic medium filling space to transmit optical disturbances, offering a coherent alternative to competing particle theories of light.