Open Philosophy 2019; 2: 657–667 *Corresponding author: Osvaldo Pessoa Jr., University of São Paulo, São Paulo, Brazil; E-mail: opessoa@usp.br Open Access. © 2019 Osvaldo Pessoa Jr., published by De Gruyter. This work is licensed under the Creative Commons Attribution 4.0 Public License. Osvaldo Pessoa Jr* A Causal-Pluralist Metatheory of Observation https://doi.org/10.1515/opphil-2019-0050 Received May 31, 2019; accepted November 11, 2019 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. Keywords: Observation, Perception, Neutral observations, Null-effect observations, Observational materialism, Sensorium 1 Introduction The use of the term “observation” in the physical sciences has led to assertions that black holes, invisible neutrinos, and molecular orbitals have been observed, raising some discussion of whether such usage is appropriate, in comparison to the more colloquial use of the term, which considers, for example, that the observation of a bear track is not an “observation of a bear”, but only evidence upon which the bear’s passage might be inferred. Another extension of the term “observation”, in neuropsychology, refers to events occurring inside the brain, such as an aura in a migraine attack. If an observation is defined as a form of perception, then the philosophical problems related to the nature of perception in hallucinations, illusions, and dreams must also be addressed by a theory of observation. The present paper is an attempt to extend the notion of observation so as to encompass the aforementioned uses in the physical sciences and neuropsychology, offering a solution to the philosophical problems of perception. The basic idea is to consider that, in an observation, the conscious observer has access to information originating at any stage of the causal chain leading to perception. But such information can only be obtained if the subject has an adequate theory to guide his inferences. Thus, all observation must involve theorization and inference. From such a general viewpoint, the colloquial sense of “observation” can be characterized in terms of the stage of the causal chain being emphasized (proximal, but outside the human body) and the level of theorization being used (low and medium levels).