Whoso remembers that, among quite simple phenomena, causes produce effects which are sometimes utterly at variance with anticipation, will see how frequently this must happen among complex phenomena. That a balloon is made to rise by the same force which makes a stone fall; that the melting of ice may be greatly retarded by wrapping the ice in a blanket; that the simplest way of setting potassium on fire is to throw it into the water; are truths which those who know only the outside aspect of things would regard as manifest falsehoods. And, if, when the factors are few and simple, the results may be so absolutely opposed to seeming probability, much more will they be often thus opposed when the factors are many and involved. The saying of the French respecting political events, that “it is always the unexpected which happens” — a saying which they have been abundantly re-illustrating of late — is one which legislators, and those who urge on schemes of legislation, should have ever in mind.
Herbert Spencer, “Specialized Administration,” The Fortnightly Review(December 1871).