When senator John McCain died last year, there was an outpouring of appreciation for his career from across the political spectrum. The praise was just as strong, if not stronger, from those who had been on the opposite side of politics from McCain as from those on his own.

There is a superficial puzzle about this. Why should people who put so much effort into preventing McCain from achieving various political goals now praise his wonderful and admirable career?

But that’s an easy puzzle. Democracy isn’t war. Though it can be shot through with martial language and metaphors, democracy ultimately requires a high level of respect between the “warring” sides. Without that, the peaceful exchange of power that characterises democracy becomes impossible. In fact, if one’s view of democracy doesn’t distinguish between electoral campaigns and artillery campaigns, that democracy will be an inherently fragile project.

Still, a residual puzzle remains. There is a great deal of variation in how much we respect and admire our adversaries. Why are some political rivals, but not others, afforded this admiration and respect? And what makes a rival worthy of esteem?

One answer can be found in the language that many centre-left people used when praising McCain. They said he was principled. By this, I take it, they meant he lived up to the principles he held. It can’t mean that he campaigned for the right principles; after all, these words came from his political opponents.

I’m not sure whether John McCain was principled. For that matter, I’m not sure if there is any good explanation of why he deserved this kind of cross-party praise. But some people do, and it is good to think about what makes them deserving. And the suggestion that we should admire our principled opponents is interesting.

At first glance, this looks like a plausible solution to the puzzle over when we should admire an opponent. An opponent may be admirable because they are principled, because they work hard to advance their sincerely held moral principles. But they are nevertheless an opponent, because we don’t share their principles, and we do not think their principles should be advanced.

But at second glance, this story can’t be right. It is too easy to be principled. Fanatics, terrorists and racists can all have sincerely and deeply held moral principles, and they can make enormous sacrifices to advance those principles. Yet that doesn’t make them worthy of admiration and respect.

It’s not even clear it makes them better in any respect. We don’t look at people who have carried out great wrongs and think “Well, at least they were doing what they thought was right.” That they thought it was right to commit these atrocities is arguably an additional mark against their character. So, it’s not admirable that bad people are principled.

What is more, it doesn’t seem to matter whether good people are principled or not. If I see someone being kind, I should admire and respect their kindness. It seems very weird to think “Oh, I bet they have a principle that says one ought to be kind, and it is very admirable that they are following that principle.” That’s both too speculative – who knows what is going on in their head – and too indirect. Acts of kindness are admirable just because they are kind, not because they conform to a principle the kind person has set for themselves.

So, if we admire our opponents, it shouldn’t be because they are principled. They may well be principled, but it doesn’t matter. It’s too easy to be principled. And since being principled is neither a redeeming feature among the wicked nor what we admire in the virtuous, we have to ask again: what makes some of our adversaries more admirable?

A better answer is that we have many different values that we try to promote through political action. We want our fellow humans to be free from oppression and also free from hunger. We want them to flourish and be free to choose how to live their lives, but also to be restricted from harming others.

Some political fights come about because others do not share our values, or because they value things that we think lack value. Perhaps they in fact positively value racial segregation, or they positively value having power concentrated in the hands of rich, white men. Few people nowadays would express such values this bluntly, or even acknowledge to themselves that this is what they value, but still their actions can reveal such disrespectable values. And there are certainly people fighting against such actions and values today.

But, crucially, not all fights are like that. Other fights arise when a plurality of values come into conflict. And in those cases, very different trade-offs can occur. Some people who really share our values make very different choices about which to prioritise, and to what degree, when those values come into conflict. And these choices might not be one-off; the people in question might systematically make different choices when there is a trade-off to be made.

That’s where you find the really admirable, really respect-worthy, opponents. There are people in politics who are promoting truly valuable ends. Or, at least, they are promoting ends we agree are valuable. They might disagree with us, perhaps dramatically, on questions of everyday policy. But their disagreements are grounded in a shared appreciation of the many and varied interests of the people affected by a policy.

To make this concrete, think about how a typical person from the centre-left should think about libertarians. The libertarian might end up disagreeing with them on many of the issues that arise in day-to-day politics. But they would be making a mistake if they didn’t appreciate the values they share with the libertarian. They would be making a bigger mistake if they didn’t value the things, like freedom from state oppression, that underpin libertarians’ philosophy.

Disagreeing with libertarian policies, as I often do, shouldn’t prevent me from admiring people who are working hard to promote a very good thing: freedom from state oppression. And this example explains why we generally admire some of our political adversaries: they are working hard to promote valuable ends, even if we think they’ve got the balance of the values all wrong.

Ultimately, what matters is not whether someone is principled, but whether they have been promoting genuinely good things. There are many ends worth pursuing, and politics is about trade-offs between values as well as clashes between people with incompatible values. When we acknowledge this, we begin to see how someone pursuing an important aspect of what is good can end up an opponent. Ideally, we’d talk them over to our side, or at least meet in the middle after listening to what the other has to say. But that won’t always happen. And when it doesn’t, we shouldn’t forget the values they are fighting for, and admire their fight.

Brian Weatherson is Marshall Weinberg Professor of Philosophy at the University of Michigan. He is the author of Normative Externalism and the co-editor of Epistemic Modality.

This article is part of the Agora series, a collaboration between the New Statesman and Aaron James Wendland. Aaron is Assistant Professor of Philosophy at the Higher School of Economics.