Vernon Bogdanor:

A.J.P. Taylor once said that we learn from history not to repeat the old mistakes. So we make new ones instead.

Paul Graham Raven:

Better technology doesn't necessarily mean thinking about what a technology does or how it does it, but about why you wanted the technology in the first place, and what you definitely don't want it to do.

Michael Hobbes:

This is the paradox: When you improve something, you change it in ways you couldn't have expected.

My favorite example of unintended consequences comes, weirdly enough, from the United States. In a speech to a criminology conference, Nancy G. Guerra, the director of the Institute for Global Studies at the University of Delaware, described a project where she held workshops with inner-city Latina teenagers, trying to prevent them from joining gangs. The program worked in that none of the girls committed any violence within six months of the workshops. But by the end of that time, they were all, each and every one, pregnant.

James Kynge:

Chinese children are taught that "diligence is a cash cow and thrift is a gold mine", while adults are warned in one somewhat humorous proverb that "going to bed early to save candles is not economical if the result is twins".