ABSTRACT
The surprise that we experience when confronted by unusual phenomena is not always in proportion to the intrinsic difficulty of their explanation. It has often happened in the history of the sciences that the curiosity aroused by a given group of phenomena owing to the apparent eccentricity of a small number, has served to emphasise how the principal difficulty did not consist so much in explaining what was strange as in accounting for what, in virtue of its being more familiar to us, we considered ‘natural’. This has been the case with the various psychological phenomena that we class under the name of “mental equilibrium”. At first sight it appears “natural” to us that a man should think and reason correctly, and on the other hand we are very astonished at the strangeness of madmen, of the “unbalanced”. Buta more mature reflection should convince us that it is much more difficult to account for mental “balance” than for its opposite.
