My son was not quite three when he first started telling us he was a boy. He had been assigned female at birth. At first my wife and I chalked it up to one of those “kids say the darndest things” comments. When he kept asserting it, we thought maybe he was telling us he preferred doing boy things — kind of a tomboy. He consistently chose toys we associate more with boys. That wasn’t a stretch.

But that wasn’t it either. He didn’t say “I want to be a boy.” He didn’t say “I want to be like a boy.” He said, “I am a boy.” And he kept saying it. Patiently. Insistently. With the directness that very small children bring to the things that matter most.

Back then we hadn’t even considered he could be transgender. The only transgender people we knew were adults. So we hadn’t really thought about gender identity emerging at this age. But Jacq knew. He didn’t have the word for it. He didn’t need the word. What he was telling us was that someone had gotten something important wrong about him. The designation made at his birth, the box he had been placed in, the pronoun he had been given — it didn’t fit. He was a boy. Not wanting to be a boy. A boy.

This episode is about what I didn’t know. And what it took to find out.

Let me be precise about the nature of my not-knowing, because it is more instructive than many of us give it credit for. I was not a man who believed transgender people were confused or disordered or mistaken. I was something simpler and far more common. I was a man who had never had a reason to think carefully about this. Gender had presented itself to me as a settled question — not because I had evaluated the evidence and reached that conclusion, but because I had never had any particular reason to look. My children had arrived, been assigned their sexes at birth, and grown into themselves. Or so I had understood it.

What my son was telling me, at age not-quite-three, was that I had been working with a model that didn’t fit the data. And I had spent my career being trained for exactly this situation.

To be a little more specific about my education, I have a bachelor’s in electrical engineering from Kettering University and a master’s in electrical engineering and optics from the University of Michigan. For more than three decades I have designed advanced aerospace systems — from satellite-based sensors and docking mechanisms for spacecraft, to optical air data systems and clear-air turbulence sensors for aircraft, to long-range atmospheric measurement systems for rocket launches and weather forecasting. Systems that must operate in harsh conditions I cannot directly observe, under conditions I cannot fully predict.

The cardinal sin in my discipline — the failure mode that ends careers and, in less forgiving metaphors, brings bridges down — is not ignorance. Every engineer operates in conditions of partial ignorance. That’s what makes the work hard and interesting. The cardinal sin is pretending not to be ignorant. It’s applying certainty you haven’t earned to a system that will eventually, under some condition you didn’t anticipate, test that certainty and find it insufficient.

When the model doesn’t fit the data, you revise the model.

My three-year-old son was data I had not anticipated. I had two choices. Force him into the model I had inherited. Or update the model. The engineering training made one of those options obviously correct. The fear — and I won’t pretend the fear wasn’t there — made it feel harder than it sounds.

The fear deserves to be named, because it was real, and because I think it is recognizable to any parent listening. I was not afraid Jacq was wrong about who he was. His certainty was transparent and total. The honest certainty of direct experience. I was afraid of what it would mean for him in the world. I was afraid of the cruelty he might encounter. I was afraid of the systems that had not been designed with him in mind. I was afraid that loving him as he was would not be sufficient armor against a world that had not yet decided how to treat people like him.

That fear is different from the manufactured fear I will spend much of this series examining — the fear that gets cultivated and deployed by political movements for their own purposes. My fear was the ancient, specific fear of a parent. That the world will be harder for your child than your love can fix.

Here’s what I learned about that fear. It is a terrible guide. Not because it’s irrational — it isn’t — but because it points in the wrong direction. The fear says: protect your child by fitting him into the world as it is. The evidence says something else entirely. Children supported in their authentic identities, who are affirmed by the people who love them, who receive the care that medicine has developed for them — those children thrive. The research is now substantial and consistent across countries, study designs, and patient populations. The fear wanted me to make my son smaller. The evidence wanted me to make the world bigger.

The evidence won.

Because alongside the fear was something else. I was urgently curious. I wanted to understand. Not because understanding was a professional obligation, though it was. Not because I had been presented with a political problem requiring a political response, though that too was coming. But because my child was showing me something I had never seen before, and it was extraordinary.

How does a child still a couple of years away from kindergarten know, with that kind of clarity and consistency, that their identity is fundamentally off? What does the developmental science actually say? What has been studied? What do the clinicians who have worked with hundreds of these kids find?

I started reading. I called physicians. I found researchers. And most importantly, I found people whose lived experiences matched our own. My wife and I attended a conference in Seattle called Gender Odyssey, organized by Aidan Key — a trans man wholly committed to bringing together communities of trans adults, families of young trans kids, and professionals from all over the world to share their stories and what they’d learned. The relief we felt was palpable. We weren’t crazy. And we certainly weren’t alone.

I learned that Jacq was not an anomaly. Gender identity typically crystallizes in children between three and five years old. Children who are consistent, persistent, and insistent about their gender identity are, in long-term follow-up research, almost universally found to have been right about themselves from the beginning. I came away with more evidence than I could have hoped for, and the confidence to press forward.

Doctors and therapists from Boston eventually joined the University of Michigan Health System a few years later. Led by pediatric endocrinologist Dr. Daniel Schumer, they started a gender clinic staffed with clinicians who had devoted their careers to exactly this. There was a substantial and growing body of evidence. When I read it without the filter of what I expected to find, it was coherent and clear.

Somewhere in that process — somewhere between the first phone call and the third research paper — the fear began to lose its grip. Not because the world had become safer. It hadn’t. But because knowledge is its own kind of courage. When you understand what you’re dealing with, you can make decisions grounded in evidence rather than managed by anxiety. You can build a plan that’s actually responsive to reality. You can be, in the engineering sense of the word, useful.

Jacq and I took this journey together, in the way the best journeys between parents and children happen. Him leading. Me following. Both of us learning the terrain as we went. He didn’t need me to already know. He needed me to be willing to find out. And the willingness to find out — the genuine, sometimes humbling willingness to discover that the world is more complex than you had understood — turned out to be the most important thing I had to offer him.

I want to use the word excited deliberately. Because I was. The science of human development. The neuroscience of gender identity. The fact that a child not yet three can know himself in a way his environment hasn’t caught up to. These are fascinating things. I went in afraid and came out curious — not the most poetic transformation possible, but in my experience, one of the most useful.

My son was not the only one who taught me. Each of my kids, more often than not through their own trials and tribulations, has exposed a blind spot in my worldview. What I discovered across these experiences is something I suspect most parents discover eventually if they’re paying attention. Children do not arrive as blank slates waiting to be written on. They arrive as themselves. Partially formed, still becoming, finding their footing — yes. But always themselves. With inner lives running on their own logic, their own perceptions of what is real, their own needs that may or may not match the ones you were ready for.

The part of the parent’s job that doesn’t get spoken about honestly enough is being a student. Not just a teacher, a guide, a standard-setter. A student. Of this specific child. In this specific moment. With this specific reality they are bringing to you. That requires sitting in genuine uncertainty. Not performing uncertainty. Not tolerating uncertainty until you can get back to certainty. Actually accepting that you don’t know — and becoming curious about what you might learn.

This, I have come to believe, is not only a skill for parenthood. It is a skill for citizenship. And it is one we are not cultivating nearly well enough.

In the spring of 2016, another parent outed our family on Facebook. This parent was running for a school board seat and had apparently concluded that the existence of a transgender child in the district was a political asset for their campaign. A torrent of accusations and conspiracy theories appeared online. Friends alerted us. I sat down that night and wrote a response. It began with the words this series is named for.

Hello, world. I’m the dad of a trans kid.

I’ve been asked many times since what it felt like to write those words. What I want to say now, that I didn’t fully articulate then, is what I was actually doing. I was not only defending my son, though I was. I was not only correcting the record, though I was doing that too. I was making public, for the first time, everything I had learned in the preceding years. Everything Jacq had been patient enough to show me. Everything the researchers at the University of Michigan had helped me understand. Everything the science said clearly that the false certainty of the attacks was choosing to ignore.

The greeting was deliberate. I addressed the world because what was happening in our school district was not really about our school district. My son’s existence had been weaponized into a political statement by someone else without his consent or mine. The response had to be an introduction. Of him. Of us. Of the truth we had spent years learning together. Here we are. Here is what is real. Here is what the evidence shows. Here is what it means to follow it honestly.

What followed — the viral spread of the post, the media attention, the legislative hearings, the decade of advocacy — was not something I planned or sought. Sarah and I describe ourselves as sleeping giants. People who did not seek this fight. Who were reasonably comfortable in our lives. Who got woken up by our son’s existence, and by the political forces that decided to target children like him, and who found we couldn’t go back to sleep. Once you know what you know, you can’t unknow it. Once you have followed the evidence to where it actually leads, pretending it points somewhere else requires a kind of dishonesty that an engineer — or a parent — cannot sustain.

Let me be clear from the beginning of this series about what kind of book — and what kind of podcast — this is. It is not against religion. I am agnostic. Genuinely, not as a rhetorical position. I do not know whether God exists, and I have arrived at that honest uncertainty after genuine reflection, not through indifference. I have found real wisdom in religious traditions. Some of my most committed allies in this fight have been people of deep faith whose convictions led them, through their own encounter with the evidence of real human lives, to stand on the side of inclusion. The movement I am proposing here cannot succeed without those communities, and I will not pretend otherwise.

The argument I am making is more specific than “religion is the problem.” The argument is that faith is not fact. That a sincerely held belief is not the same as an empirically verifiable claim. And that the confusion of the two, specifically in the context of governance, has costs that fall most heavily on the most vulnerable. I am not asking anyone to abandon their faith. I am asking for an agreement about jurisdiction. The laws governing everyone should be grounded in evidence everyone can, in principle, evaluate. Not in doctrines explicitly designed to be beyond evaluation.

This is, I think, a modest ask. It is apparently also a radical one. Which tells us something important about where we are.

I write as the father of a transgender son. As an engineer trained in the discipline of honest uncertainty. As an agnostic who has made peace with not knowing — and who believes that peace, that willingness to remain open to what the evidence shows, is not weakness. It’s intellectual integrity. And as a later-life advocate who came to this work not young and primed for it, but gradually, reluctantly, and at real personal cost — because my son needed me to. And because the truth, once you have seen it clearly, doesn’t allow for comfortable silence.

Hello, world. This is what I’ve learned. I hope you find it useful.

Sign up on this site to receive updates on the soon-to-be-published book, “Hello, World, I’m the Dad of a Trans Kid: The Case for Curiosity in a World Addicted to Certainty.” If podcasts are your thing, please check out the podcast series of the same name.