A few years ago at a party I was explaining some interpretive debate about Marx to a friend. Marx, I was saying, might have believed A, or he might have believed B, and there is evidence on both sides. My friend objected: what does it matter? Surely we should talk about whether A or B (or neither) is correct, not about which of them a guy from the Rhineland who died almost 150 years ago believed.
Prima facie, this is a pretty good objection. It is a good objection because a lot of people who study the history of ideas don’t seem to realize that it is an error to believe something merely because someone whom you consider to be wise believed it.
But I think the history of ideas is worth studying. Some of the reasons for this are pretty complicated (see here and here), but two are simple:
1. You might be able to use the ideas
In historical study, you might come across some ideas that you like. For instance, much of A Theory of Justice involves Rawls’s adaptation of Kant’s ideas.
Why study the history of ideas to get access to ideas from the past rather than just going with the stereotypical versions of various writers that you get from high school, reading general histories, or watching cartoons? Because, and this is a claim I can’t prove here, the primary sources by writers who are in the canon tend to be far more complicated than the memes about them that circulate in the culture. For more than two hundred years, economists across the political spectrum have drawn inspiration from reading Adam Smith. You could look at that and say, well, no point reading Smith if people can’t even agree what he said. But I think a better way of looking at it is that Smith helps economists of various persuasions set aside their normal methods of work, look at things from a more abstract point of view, try to transpose some old concepts into their own paradigms, and see if their ways of thinking can answer questions that Smith leaves open.
Some historians, most famously Quentin Skinner, object that it is illegitimate to look to the past for concepts and arguments that you can pick up and use for your own purposes. But Skinner himself was unable to resist the temptation to revive what he calls the “neo-Roman” conception of liberty and apply it to contemporary political philosophy in his book Liberty before Liberalism (which I will probably post some notes on soon). In general, I don’t see what the problem with reading canonical thinkers for inspiration on contemporary questions could possibly be (unless it is that there are more pressing uses of time).
2. You might better understand people in the present
Often people are adherents of religions or ideologies that are written up in canonical works. If you want to know what those people will do, how to negotiate with them, or how to stop them, it may be worthwhile to study those works. Graeme Wood’s article “What ISIS Really Wants” includes some discussion with Bernard Haykel about how ISIS fits into the broader tradition of political Islam. There are a lot of reasons you might need to know what ISIS really wants, and studying the history of ideas could be part of finding out.
Political leaders sometimes espouse an ideology merely because it would look bad if they openly admitted that they were just in it for power. However, even in such a situation, the ideas that a leader claims to believe constrains his actions. It is ceteris paribus harder to improve relations with an ancestral enemy if you got elected by claiming to be a nationalist firebrand. This is true regardless of how you privately feel about nationalism. And if an ideology is socially dominant but not always believed in private, it might still guide action. People won’t want to imply by their actions that they no longer believe in the ideology. That closes off certain paths to them. Having this sort of information about a partner or an adversary is useful.
There also might also be some overlap between reasons 1 and 2. For example, you could set out to learn about how to stop religious extremism and end up converting to Islam.