There is a famous slogan in machine vision, attributed (wrongly, it seems) to Max Clowes: ‘vision is controlled hallucination’. The aim of my paper is to argue that perception is controlled mental imagery. This is not that significant a diversion from the original Clowes dictum, given that what I mean by mental imagery, following Kosslyn and Jeannerod, is 'perceptual processes that are not triggered by corresponding sensory stimulation in the relevant sense modality’ and hallucinations would clearly qualify as mental imagery according to this definition. Perception is mental imagery inasmuch as (almost) all perception involves the exercise of mental imagery: of perceptual processes that are not triggered by corresponding sensory stimulation in the relevant sense modality. But it is controlled mental imagery inasmuch as these perceptual processes are most often combined with and tweaked by sensory-stimulation-driven perceptual processes. The main claim of this paper is that perception, as we know it, is the combination of the two: it is controlled mental imagery.