In 1868, C.S. Peirce argued that there is no power of intuition in the sense of a cognition unconditioned by inference, and no power of introspection, intuitive or otherwise, and that awareness of an internal world is by hypothetical inference from external facts. Introspection and intuition were staple philosophical tools at least since Descartes. He argued that there is no absolutely first cognition in a cognitive process; such a process has its beginning but can always be analyzed into finer cognitive stages. That which we call introspection does not give privileged access to knowledge about the mind—the self is a concept that is derived from our interaction with the external world and not the other way around (De Waal 2005, pp. 7–10). At the same time he held persistently that pragmatism and epistemology in general could not be derived from principles of psychology understood as a special science: what we do think is too different from what we should think; in his "Illustrations of the Logic of Science" series, Peirce formulated both pragmatism and principles of statistics as aspects of scientific method in general. This is an important point of disagreement with most other pragmatists, who advocate a more thorough naturalism and psychologism.