Life, they urge, would be intolerable if men were to be guided in all they did by reason and reason only. Reason betrays men into the drawing of hard and fast lines, and to the defining by language -- language being like the sun, which rears and then scorches. Extremes are alone logical, but they are always absurd; the mean is illogical, but an illogical mean is better than the sheer absurdity of an extreme. There are no follies and no unreasonablenesses so great as those which can apparently be irrefragably defended by reason itself, and there is hardly an error into which men may not easily be led if they base their conduct upon reason only.
Reason might very possibly abolish the double currency; it might even attack the personality of Hope and Justice. Besides, people have such a strong natural bias towards it that they will seek it for themselves and act upon it quite as much as or more than is good for them: there is no need of encouraging reason. With unreason the case is different. She is the natural complement of reason, without whose existence reason itself were non- existent.
If, then, reason would be non-existent were there no such thing as unreason, surely it follows that the more unreason there is, the more reason there must be also? Hence the necessity for the development of unreason, even in the interests of reason herself. The Professors of Unreason deny that they undervalue reason: none can be more convinced than they are, that if the double currency cannot be rigorously deduced as a necessary consequence of human reason, the double currency should cease forthwith; but they say that it must be deduced from no narrow and exclusive view of reason which should deprive that admirable faculty of the one-half of its own existence. Unreason is a part of reason; it must therefore be allowed its full share in stating the initial conditions.

Samuel Butler