They cannot convince the mind, but they do cloud it.

Just as it is the latest fad [of Freudian psychoanalysis] to prove that everything is sexual, so it was the last fad [of Marxism] to prove that everything was economic.  . . .  These fads fade very fast, and it may seem hardly worthwhile to prick bubbles that will burst of themselves.  Nevertheless, there is one consideration that makes it worthwhile.  It is a character of all these manias [from Darwin, Marx, and Freud] that they cannot really convince the mind, but they do cloud it.  Above all, they do darken it.  All these tremendous and rather temporary discoveries have had the singular fascination that they were not merely degrading, but were also depressing.  Each in turn leaves no trace on the true and serious conclusions of the world.  But each in turn may leave very deep and disastrous wounds and dislocations in the mentality of the individual man.

G.K. Chesterton, “The Game of Psychoanalysis”, Century Magazine, May 1923, quoted in Dale Ahlquist, Common Sense 101, p. 110.