That men do not learn very much from the lessons of history is the most important of all the lessons of history.
If one is not oneself a sage or saint, the best thing one can do is to study the words of those who were.
The inconveniences and horrors of the pox are perfectly well known to every one; but still the disease flourishes and spreads. Several million people were killed in a recent war and half the world ruined; but we all busily go on in courses that make another event of the same sort inevitable. Experientia docet? Experientia doesn't.