2 th - century theories of perception paradigms literally perceive different worlds The opposing view is that observation is theory-neutral and it can serve as an impartial tribunal to adjudicate clashes of opinion In philosophy of mind, this disagreement later generated two versions of constructivism Reacting to the idea that observation is theory-laden, Jerry Fodor published an influential work that denied that perceptual inferences are affected by other mental states (Fodor 1983; 1984) Fodor proposed modularity The modular thesis includes a number of claims, but one of the central claims is that perceiving is importantly isolated from thinking and believing Perceptual processes are largely immune to influence from outside of perception, such that what we perceive is pretty constant through time and across world-views Deniers of modularity claim that perception is ‘cognitively penetrable’ (Churchland 1988) Perception is influenced by background knowledge and expertise such that the same subject may perceive the world differently at different times as a function of a change in beliefs Along similar lines, different subjects may perceive the world differently as a function of their differing theoretical convictions Work on cognitive penetrability and on the modularity of perception is ongoing with philosophers interested in understanding the epistemic consequences of thinking of perception as cognitively penetrable (Raftopoulos 2009; Siegel 2012) Despite the popularity of constructivism in the second half of the 20th century and the beginning of the 21st century, an alternative position – reminiscent of work in the continental tradition in philosophy – emerged and is now popular in embedded and embodied approaches to mental activity This is the ecological view of perception that I briefly discuss in the next subsection 2.3 Ecological perception The major alternative position to constructivism rejects the computation- and representation-heavy approach to perception in favor of a more ‘ecological’ way of understanding the perceptual process In explaining why we see the world as we do, the ecological view says that we should focus on the way the world is The main precursor of this type of position in psychology is J J Gibson (Gibson 1950; 1966; 1979) Initially influenced by Gestalt Psychology, Gibson’s work is primarily a reaction to Helmholtz’s ideas Gibson stressed two elements of the perceptual act First, that perception happens over time, and in a moving and exploring, body Second, that the information available in the natural environment and in sensation is rich and not inadequate as supposed by constructivism In vision, the information is present in what Gibson calls the ‘ambient optic array’ which is available to, and picked up by, our eyes The ambient optic array contains a number of invariants that allow the perceptual system to figure out the distal layout Slanted surfaces of various kinds, for example, project images on the retina that have characteristic texture gradients (Gibson 1950) Perceivers can use such gradients to see the slant and depth of surfaces in the world 117