Almost everyone believes the following: Vaccines are a good and necessary part of medicine.

Some people, and more people every day, believe this, too: Those who don't believe in the virtues of vaccines — anti-vaxxers — are ignorant and dangerous lunatics, possibly evil.

I spent most of my life believing that. During my early 20s, I lived in the skeptic blogosphere, a mid-2000s constellation of internet communities theoretically organized around highly charismatic bloggers, vloggers, and other intellectuals. In practice, however, these groups were centered on a more basic principle: hostility toward anyone and anything it deemed "irrational." It was then and is still now a very white, male, and defensive place.

It was there that I developed a deep antipathy toward the anti-vaccination movement. It wasn't that I knew they were wrong about vaccines. It was more than that. I believed myself intellectually and morally superior to those people, and I reinforced that belief each time I left a comment or watched a vlog or republished a snarky article on the subject. I mastered a face, a kind of appalled, disapproving look for any time anybody even broached the subject of vaccine skepticism.

Then I married an anti-vaxxer.

Here's what I learned.

1) Anti-vaxxers aren't paranoid misfits

I met my wife nine years ago. I wanted to take up swing dancing and decided to take a private class to get over some of my anxiety. She was the teacher who picked up the phone when I called.

I was immediately attracted to her, but at the time she was engaged to her dancing partner, the father of her daughter.

So at first we built a platonic friendship. We spent time together. We bonded over our mutual interest in dancing. I had known her for more than a year the first time she mentioned that her daughter was not vaccinated.

What do you do, then, when someone you believe is both smart and sensible comes to a conclusion you find completely wrong? Does that person stop being smart at that precise moment?

My time reading (arrogant) skeptic blogs had convinced me of my moral and intellectual superiority. I believed that because I was a smart, sensible, and empathetic person I could see the value of vaccines. Yet here this woman was. I knew she wasn't dumb — in fact, I thought she was very insightful. I knew she wasn't dangerous or conspiratorial — we had talked for days about how we care about people, and the society we live in, and what it means to be human. I already trusted her.

Did I have to completely reassess my opinion of this person? Did I have to examine my own biases and mental caricatures, decide that anti-vaxxers are people too?

Well, no. I did what most people did: opted for cognitive dissonance. I decided it wasn't worth getting into a fight over, that she could be my friend and have weird opinions about vaccines at the same time. Even as she broke up with her partner, and I broke up with mine, and we found ourselves spending a lot of time together, I ignored the issue. The subject of vaccines came up once or twice over dinners, but so what? I could see she loved and cared deeply for her daughter. She was someone I admired and respected and was beginning to love. Vaccines didn't get in the way.

And, of course, I believed that if we spent enough time together, I'd eventually change her mind.

2) It's all about fear

It's not that anti-vaxxers are stupid, or that they're corrupt. It's that they're afraid.

This is the beating heart of any real discussion about anti-vaxxers. It's impossible to understand their position without considering the amount of fear that goes into the anti-vaccine narrative, and considering how people construct and deal with fear.

I believed that if we spent enough time together, I'd eventually change her mind

Now, you might think that a fear is a fear and public health is something else — and you might be right. That's the rational point of view. But then, how rational are your own fears?

Maybe you're afraid of heights. Maybe it's spiders. In either case, you're lucky: Coping with your fear the way most people do — avoidance — doesn't come at a cost to others. But vaccines only work when everyone buys in. Public health depends on anti-vaxxers confronting their greatest fears for the benefit of others.

For people who don't share their fear, it's very easy and convenient to demand that anti-vaxxers just suck it up and take the shot. I wish they would, too. But we'll never get there by bullying them, by insulting and demeaning them and refusing to take the fact of their fear seriously, even if there isn't much that's serious in its content.

That's hard to do. Have you ever tried to stare a loved one into the eye and tell her you are going to put her child in danger?

Despite initially avoiding the subject, I decided, after we were married, that I should convince my wife to vaccinate her daughter. Vaccines are good, after all. Vaccines are safe. Measles outbreaks had been on the news — what better time to raise the subject?

But when I did, I realized that from her perspective, all of my confrontational reasoning sounded like me asking to point a gun at her daughter and have her trust that it was full of blanks. Looking into her eyes, I realized her trust in me was threatened. She asked why I would do that to a child. All of my insistence that vaccines are safe didn't matter. Go tell arachnophobic parents that you must put spiders on their child because society depends on it, and see how that goes. The benefits of getting the shot, expressed in the abstract, simply could not overpower the immediate, disarming fear.

So I backed down. The anti-vax position was not a deal breaker for me, but suggesting that we should expose her daughter to grave dangers for no good reason was a deal breaker for my wife. I loved my wife. I had no desire to end things. Yes, I think it was very important for her daughter to receive vaccines — but it's not as if my wife would have changed her mind over a breakup fight.

I backed down and resolved to have that conversation in less confrontational terms when the opportunity arose.

3) If you think something is dangerous, it's logical to avoid it

My wife is one of the smartest, most sensible people I know. So what do smart, sensible people do when they perceive a threat? They do the smart, sensible thing: take precautions and warn others.

What do you think anti-vaxxers believe they're doing?

Again, it's easy to dismiss the worries of anti-vaxxers as irrational and chalk up their activism to paranoid behavior, but this misses a crucial point: The reasoning, once you accept the big, unsubstantiated premise, is valid. It isn't even that far-fetched, if you don't think about it too hard: There are some heartbreaking precedents that feed this logic. Lead paint, tobacco, bloodletting — every time we feel the urge to reply, "But vaccines are safe, everyone knows that," we ought to remember that the same sentence has been said, earnestly and confidently, about things that absolutely were hazardous.

Go tell arachnophobic parents that you must put spiders on their child because society depends on it, and see how that goes

If you've come to believe that vaccines are dangerous, then anti-vax behavior follows almost rationally. If we want to reach these people, dismissing their logic as ridiculous or fringe is the worst strategy. It plays right into the anti-vaccination narrative: that they are the "only sane ones," warning the careless masses about a very real and hidden danger.

My wife (and her family) sincerely believes that though her worries are being recognized as irrational, they aren't. It's easy to imagine how the very first person to notice the dangers of something ubiquitous, like lead, was dismissed by her peers as irrationally afraid — and to imagine you might be one of these people. The first anti-lead folks were called cranks — until they were proven right.