"The crash" is a phrase sometimes used in socialist writings; perhaps first coined by Eduard Bernstein, in the 19th century. The phrase is commonly understood as referring to a metaphor, one of modern industrial society as a train; one which is going to derail and crash. Theodore Kaczynski is notable for encouraging terrorists to cause such a "crash", arguing that the sooner the crash comes, the less severe it will be. Many socialists argue that the crash will occur when global oil supplies run out, when global warming and pollution reaches a certain critical point, or when global population exceeds carrying capacity.