Perception is reformulated as a functor from sensory input to perceptual synthesis. Sensory input provides “patches”—local data from different sense modalities and attentional frames. Perceptual synthesis glues these patches into a unified perceptual experience. The perception functor P : ℂateg{Sens} → ℂateg{Exp} maps sensory covers to experiential sections. Illusions and hallucinations are diagnosed as gluing failures: the patches do not cohere, but the perceptual system forces a section anyway. The direct-versus-indirect realism debate is dissolved: perception is mediated (by the functor) but faithful (the functor preserves structure). The perceiving organism is not a passive receiver but an active section-constructor.