I think a lot of political questions hinge on what's possible, and also what the consequences of policies are. If someone says "I think we should arrange marriages instead of letting individuals pick," then the immediate questions to settle are 1) will people allow such a policy to be put in place / comply with it, and 2) what will the consequences be?
(There's also the "does this align with principles" deontological question, but this is relatively easy to answer without looking at the past or present so I'll ignore it.)
And the past provides our primary data source to answer those sorts of questions. Yes, we can imagine multiple different causal effects of attempting to arrange marriages, but how those interplay with each other and shake out is hard to know. But other people tried that for us, and so we can investigate their experiments and come to a judgment.
The problem I see in using the past as evidence is that the further we go from our era, the more what we know is mostly made up.
True, we have documents and evidence and so on, but they only paint a relatively sketchy picture of what the society was, we mostly made up the details in a reasonable manner. Plus we don't get any statistical data on things like happiness, income, etc.
The risk of mistaking noise for signal is so high that it's probably worth throwing it all away, especially when the starting point of the conversation is "People were happier / sadder in xth century, so we should / shouldn't do as they did".
How can you possibly know?
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
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