Koenderink claims that most perception researchers mistakenly believe in an objective reality observed by an 'All Seeing Eye.' This assertion stems from his metaphysical idealism, which has weaknesses including dualism and foundationalism. Arguments from modern philosophy of science support the existence of an objective material reality. Koenderink's enactivism is contrasted with his idealism, and phenomenology and cognitive science are shown to be complementary rather than mutually exclusive.
Illusions are often defined as perceptions that deviate from an objective, common-sense reality, but some recent arguments claim this definition is invalid because external reality may be a fiction or cannot be truly represented by our senses. This paper first warns, drawing on George Orwell, that denying objective reality risks suppressing independent thought and critical evaluation. It then argues that anti-realists mistakenly assume their opponents hold a reductionist metaphysics where only fundamental physics is real. Instead, a non-reductive metaphysics ascribes real existence to multiple levels of dynamic systems—from subatomic to ecological—making objective reality partly accessible to our senses and allowing a definition of illusions as deviations from veridical perception.
Enactivism, a leading approach in the philosophy of perception, is metaphysically ambiguous because it claims to avoid both idealism and realism while incorporating elements of each. An earlier attempt to resolve this ambiguity fused enactivism with phenomenology and the mathematical concept of symmetry breaking, but this solution is not entirely successful. Adding a multi-level, non-reductive metaphysics, such as Informational Structural Realism, is proposed. On this view, perception involves causal transfers of information at different levels within a hierarchy of meaningful structures that constitute physical reality. Phenomenologists may use 'perception' metaphorically across all levels, though realists need not.