This paper suggests that wave-particle duality and light-speed constancy may be homologous phenomena. The obvious wave-particle duality of light has long plagued the world of physics, and no explanation of the rationale of its operation has been proposed to date. Similarly, the light-speed constancy is also deemed an inscrutable puzzle in the physics community. Constrained by thinking in the materialist paradigm, scientists hesitate to examine quantum phenomena from an idealistic and non-material perspective, which might thus lead to the loss of a great opportunity for shifting science paradigms and initiating scientific revolutions. A scientific revolution mostly originates from the changes to people's ”visual angles” or viewpoints. If light-speed constancy and wave-particle duality are both an observer's ”manifestation of the mind”, then the ”observer” in the special theory of relativity and the ”observer” in quantum mechanics will mean the same-the observers in these two theories both unconsciously create a reality of their observations.