When Two Become Depth Close one eye, then open it and close the other. Notice how the world shifts—not dramatically, but subtly, like a whisper of displacement. Your thumb, held at arm's length, appears to jump against the background, revealing a secret your singular gaze could never detect. This is parallax: the illusion of movement born not from motion itself, but from the marriage of two perspectives separated by the smallest distance. It is how depth emerges from duality,