This article proposes a new reading of Edgar Allan Poe’s two short stories ‘The Sphinx’ and ‘Mesmeric Revelation’. The moth/monster conversation in ‘The Sphinx’ dramatizes Poe’s speculation of the world. The monster-like cosmos is mysterious and elusive, however human beings endeavor to contain and stabilize it into the hierarchy of human knowledge. ‘Mesmeric Revelation’ goes beyond the surface stability and unearths a hidden world of becoming. This process also marks a progression from anthropocentrism to posthumanism. In this posthumanist world, the decentering of human beings enables the equality of multiple species and their harmonious symbiosis. Poe’s hypothetical world of particles further consolidates this posthumanist reading: all things originate from indivisible particles, and particles are in a constant process of becoming and coalescing, capable of infinite potentialities. Once the particles are perceived by human organs, they will configurate into reality in accord with human idiosyncrasy. ‘The Sphinx’ accentuates the scientific aspects of moth/monster, and ‘Mesmeric Revelation’ highlights the mysterious dimensions of the issue; together they outline the obscure path from anthropocentrism to posthumanism in Poe’s epistemology.