Merleau-Ponty is best known for his positive account of the bodily nature of perception. Just as crucial to his phenomenology, however, is his negative critique of the ways in which traditional theories tend to misdescribe perception abstractly at the outset, without considering the ways in which it is constituted by the concrete structures and capacities of the body. Specifically, two chief misconceptions loom large, like Scylla and Charybdis, on either side of an adequate account of perceptual experience, threatening to obscure its distinctive character. They are what Merleau-Ponty calls “empiricism” and “intellectualism”, and they remain stumbling blocks, perhaps perennial temptations, for theories of perception today.
Empiricism is any view that conceives of perception as based on non-intentional qualitative sensory content – sensations, sense data, so-called “raw feels”, qualia and so on. Merleau-Ponty's critique of empiricism is twofold. In the first place, he argues, empiricism is descriptively wrong: ordinary perceptual awareness simply is not an awareness of sensations, but of things out in the world – people, situations, events. Second, empiricist theories are incoherent, for the resources they have at their disposal for describing pure sensory content make sense only if we take for granted the full-blown perceptual phenomena they are meant to explain.
The charge of descriptive wrongness is fairly straightforward. As Merleau-Ponty says, the concept of sensation “corresponds to nothing in our experience” (PP: 3). What we see are not mere sense data or qualia, but people and things, and often the empty gaps and spaces between them, as well as what the psychologist J. J. Gibson calls “affordances”, for example paths, obstacles, barriers, brinks, steps, slopes, shelters and tools (Gibson 1979: 36–41).