In a passage near the crescendo of Book I of The Treatise of Human Nature, David Hume writes, “the intense view of these manifold contradictions and imperfections in human reason has so wrought upon me, and heated my brain, that I am ready to reject all belief and reasoning, and can look upon no opinion even as more probable or likely than another…[I] begin to fancy myself in the most deplorable condition imaginable, inviron’d with the deepest darkness, and utterly depriv’d of the use of every member and faculty…. [S]ince reason is incapable of dispelling these clouds, nature herself suffices to that purpose, and cures me of this philosophical melancholy and delirium, either by relaxing this bent of mind, or by some avocation, and lively impression of my senses, which obliterate all these chimeras.”  (He goes on to play backgammon.)

The delirium Hume ascribes to himself is the effect of human reason and a kind of second order reasoned reflection [“the intense view”] of it. (Recall also this post.) It’s important for what follows that the ‘contradictions and imperfections’ in human reason are not, what we might call, ‘formal’ contradictions and imperfections or biases in reasoning. It’s not as if Hume is claiming that the syllogistic apparatus, or — to be closer to Hume’s own interests and our present ones — the (inductive) probabilistic apparatus is malfunctioning in his brain. Rather, his point is that a very proper-functioning (modular) formal and probabilistic apparatus generates internal, even cognitive tensions, especially when it reflects on its own functioning and the interaction among different cognitive faculties/modules/organs. [click to continue…]