Abstract
An extended definition of “observation” is developed in order to account for the usage in the physical sciences and in neuropsychology. An observation is initially defined as a perception that has a focus of attention and is guided by theoretical considerations. Since the focus may change, one adopts a pluralist position according to which the object of perception may involve any stage of the causal chain that leads to perception, such as the source of light or sound, the obstructions, the medium or even the receptor. The “neutral” observations of the empiricists are seen as involving only low-level or medium-level theorization. Examples are examined, such as a lunar eclipse, the rainbow, and observations mediated by instruments, whose “artifacts” are considered observations of the instrument itself. One also defines null-effect observations. Observations of photographs and drawings may be considered either the observation of a printed sheet of paper or the observation of the pictured object or people. This causal-pluralist metatheory of observation also accepts that one may “observe light”, observe the retina, and observe parts of the brain which are outside the region of the “sensorium”. Illusions and hallucinations are analyzed within this “observational materialism”, which considers that qualia are self-observations of the brain. Criticisms that the approach is too wide in scope are analyzed in the conclusion.