To learn how to live, we need to (among other things) discover patterns between behavior and consequences. Likewise, if we acquire knowledge of this sort it needs to be connected to what we already knew in order to be a lasting addition to our tree of knowledge.
The problem is that we only accumulate such knowledge very slowly: the occasions on which we truly learn something about why our behavior had the results it had are rare. Hence, building a solid trunk of practical knowledge is a lengthy process.
To speed this up, we should study history.
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