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http://dx.doi.org/10.1037/13701-018
We have, so far, taken for granted the existence of consciousness, and the fact that there are subjective phenomena which we, as comparative psychologists, may study. We have also proceeded throughout on the assumption that subjective phenomena admit of a natural interpretation, as the result of a process or processes of development or evolution, in just the same sense as objective phenomena admit of such interpretation. The question now arises: If consciousness exists, and if consciousness, as we know it, has been evolved, from what has it been evolved? (PsycINFO Database Record (c) 2016 APA, all rights reserved)