I am currently reading Antony Beevor's The Fall of Berlin 1945. I sometimes think one cannot know enough history. Other times I doubt the good of it. What's the use of knowing the (supposed) facts of the past? Does George Santayana's oft-quoted and thoughtlessly repeated line supply an answer? "Those who cannot remember the past are condemned to repeat it." It is usually interpreted to mean that it is necessary to remember the past in order to avoid repeating its mistakes. (Whether this is its meaning in context is a further question.) Unfortunately, it is not sufficient: one can remember the past and still repeat its mistakes if one is unable to apply its message to the present, or if one is incapable of extracting any message in the first place.
For example, is Iraq another Viet Nam? The typical leftist will say yes, the typical conservative no. Indeed, lefties were using the 'Q' word -- 'quagmire' -- before the U.S. incursion. They knew what the upshot had to be and they worked to insure that the historical logic unfolded in the right way. Leftists and conservatives who agree on the bare historical facts regarding the Viet Nam war -- and that itself is a lot to agree on -- can easily differ on their meaning and 'lessons' and thus on their relevance to the present.
Or consider the question of appeasement. We conservatives are quick to point out that genuine peace, a peace worth having, cannot be obtained by appeasement of malefactors. We cite Neville Chamberlain, Munich, 1938. Many lefties will agree. Here is the Spartacus take on Chamberlain, Hitler, and appeasement. But does the 'lesson' apply to Saddam Hussein? Or to Mahmoud Ahmadinejad, who is eager to get his hands on nukes and who many times has clearly stated that he wants the destruction of Israel? Is there a generalizable lesson -- e.g. Never appease dictators -- that can be extracted from historical particulars or is grubbing in such particulars the best we can do?
Interim conclusion: Knowledge of history won't save us. What we need to know is the meaning of history. But that is not something historians are in a position to deliver. (I am not saying that philosophers are in a position to deliver it.) Even if we get all the facts right as to who did what when and to whom, of how much use will that be?
Even though every era is different, we can, in the same way that anthropologists can extract "human universals" by a comparative study of cultures,do the same along the "time axis" by looking at how our culture has responded to past crises, which in turn allows us to separate the merely temporal responses from what is constant, and then to extrapolate usefully to the present and future.
As Mark Twain said: "History does not repeat itself, but it rhymes."
What I am questioning are these 'useful extrapolations.' Can you give me one? Something useful, not trite. History teaches homo homini lupus, but we already knew that.
I do think there is much to be learned from history, at least in the form of broad trends and patterns, if not so much the sort of detailed and prescriptive "dos" and "don'ts" that I think people often have in mind when they cite Santayana's aphorism. Jared Diamond's books, and the excellent Nonzero, by Robert Wright, are good examples of the sort of thing I mean.
But surely, even concrete, practical lessons must abound. Just off the top of my head, here's a good one: don't invade Russia in the winter!
I don't want to go off half-cocked - your question is a serious one - but as two other examples, I'd say also that history teaches us that liberty is conducive to prosperity, and that large-scale collectivist social engineering is not.
I'll say this, too - the study of history can be an immensely rewarding human activity in its own right, regardless of its predictive power. Churchill's six-volume History of the Second World War is, in my opinion, one of the greatest works ever written in English.
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