ABSTRACT
The psychology of thought provides absolutely nothing to extend logic or mathematics nor yet to help us better to understand their bases in a way that would satisfy an expert in the fields. The fiction of the malicious demon can be compared with a 0-level psychophysics; in it the perceptual arrangement of the world for a given observer in a given instant depends on the actions that are directly impressed by the wicked intentions of the demon who, given that he is very powerful, controls every single, even minimal, part of that arrangement. Unconscious judgment is in a later position relative to that of the psychophysical transformation because it is only there, according to the Helmholtzian view, that it can be used to explain deviations from that law: it was invented to that end and so that must be its position.
