What If?

"Others suffer from a different problem. They are hopelessly speculative, because they depend on wildly elaborate causal chains that are best treated as the 
exercise of an active imagination. Some counterfactualists suggest that if some apparently trivial change had occurred, large consequences would follow ('the butterfly effect,' made famous by a short story by Ray Bradbury). As a matter of logic, it may not be possible to rule out such elaborate causal chains, but they require a large number of contingencies to come to fruition (and a large number of other contingencies not to do so). Much of Evans’s exasperation is reserved for narratives that fall into this category. As 
examples, consider Tuchman's suggestion that if Mao Zedong and Zhou Enlai had met with Franklin Delano Roosevelt in the 1940s, the wars in Korea and Vietnam might not have happened, or Parker's claim that if the Spanish Armada had successfully landed in England in 1588, Philip II would have established Spanish rule in North America. OK, maybe—but who could possibly know?"


Cass R. Sunstein in The New Republic reviews Richard J. Evans's Altered Pasts: Counterfactuals in History.