2 th - century theories of perception available for discovery Rather than postulating internal states that represent information, Merleau-Ponty thought that such representations are implicit in the subject’s own dispositions to move In sum, when considering perception as a process, the 20th century saw the emergence of three theories of perception Gestalt psychology was prominent in the first half of the century, while constructivism dominated the second half, with ecological approaches serving as a plausible competitor The century also saw the emergence of intense cooperation between philosophy and disciplines such as psychology, computer science and linguistics Conclusion In this chapter, I traced the history of theories of perception in the 20th century by considering perception under two guises If we focus on perception as a relation, then I suggested that the 20th century has been preoccupied with defending realism and physicalism If we regard perception as a process, then the century was dominated by interaction between philosophy and the emerging cognitive sciences The first half of the century saw the rise of Gestalt Psychology, while the second half saw the emergence of two views, one centering on internal procedures, and one focusing on environmental interactions Notes For help and advice with this chapter, I thank Tim Crane, JJ Dinishak, Jon Ellis, Dan Guevara, Rasmus Grønfeldt Winther, Amy Kind and Samantha Matherne, whose knowledge of history helped a great deal Although widely used, the term ‘physical’ is hardly ever spelled out in philosophy of mind Some contrast ‘physical’ with ‘mental’ (which seems unfortunate since the mental would then be non-physical by definition) Often ‘physical’ is synonymous with ‘mind-independent’, ‘material’, ‘non-spiritual’ and occasionally with ‘causally efficacious’ Physicalism was initially a doctrine about the language of science (see Crane, this volume) Thanks to Samantha Matherne for this reference Martin (2003) notes that the concept of sense-data had already been used in the late 19th century, in the United States by Royce and James For the argument from illusion, see Ayer (1963: pp. 3–11), and Hume (1748) For perspectival variation and time lag of the kind that occurs when we perceive no longer existing stars, see Russell (1912) Martin (2003) points out that whether this charge against sense-data theory is on point can be questioned Martin argues that both Broad and Price were aware of the intentionality of perception G E Moore (1903) is an early precursor of transparency Thanks to Amy Kind for this pointer For deniers of transparency in some of its formulations, see Block (2000) and Kind (2003) I think that this type of problematic for sense-data theory is raised in Sellars 1956 and it is also a point pressed by Wittgenstein 1953 119