I do not feel obliged to believe that the same God who has endowed us with senses, reason, and intellect has intended us to forgo their use and by some other means to give us knowledge which we can attain by them.
— Galileo Galilei

I have a confession to make: I’m a 30-year-old man, but until a few years ago, I had no real understanding of the theory of evolution.

Ah, it feels good to get that off my chest.

I’m sure I must have been taught evolution in school, but I have almost no memory of those lessons. I suspect that I intentionally didn’t pay attention.

Why? Because I was a Christian. And Christians don’t believe in that kind of thing (or so I was told).

If you had asked me as a teenager, I would have told you that evolution was the idea that humans evolved from monkeys, that there was something about peppered moths from London, that Charles Darwin invented it, and most crucially, that it was unproven. There was a mysterious missing link that nobody could find, and the idea that fish just grew legs one day and started wandering about on the land seemed ridiculous.

My own belief seemed much more reasonable. The whole world and everything living in it was created by God in seven days. Maybe some species adapted to their environments slightly, but other than that, not much changed. This creation event happened around 6,000 years ago, as laid out in the Genesis story at the beginning of the Bible.

I would point to the complexity of life as evidence for my beliefs: Just look at the bumblebee (which shouldn’t even be able to fly!) or the incredible mechanics of the human eye. Even Darwin, on his deathbed, said he didn’t believe in evolution. Sure, we’ve dug up a few strange-shaped skulls lying around, but they could easily be human skulls that just got mashed up a bit.

All of this was enough to keep me insulated against evolution as a concept. I had no idea how full of wrong assumptions and plain lies those last three paragraphs actually are. But this is about more than just evolution. It’s about how we think. It’s about how we form ideas about the way our universe works.

It’s about how I could live most of my life so far having no idea about some of the most important and incredible discoveries that humans have ever made. It’s about two foundational ways of looking at the world around us: religion and the scientific method.

Science Isn’t Evil

Looking back, my view of science growing up was slightly skewed.

All illustrations: Jon Headley; first appeared at theallowed.com

Growing up in an evangelical church, I was taught that capital-S Science was our enemy. The main aim of Science was to disprove Christian beliefs, to convince others that there was no God. Science would do anything to achieve that goal: skewing evidence to suit their biases, ignoring obvious holes in logic, and making absurd assumptions about the world to avoid having to acknowledge the Bible was true.

It’s an attitude I grew accustomed to as a teenager: Science is a threat, and if you pay too much attention to Science, it could cause you to doubt your faith and become eternally separated from God. Of course, some little-s science was all right. We had a kind of “line of acceptable science” that allowed us to enjoy the fruits of technology and marvel at discoveries that didn’t directly threaten our worldview. Beyond that line, there were three big lies that Science had introduced to the world, and these were especially dangerous:

Luckily, I had ready-made answers for all these things.

The Big Bang? No way. How could something just appear out of nothing? And how could everything we see today come from an explosion? It’s like a tornado blowing through a scrapyard and accidentally assembling a Boeing 747. Impossible.

And saying the Earth was billions of years old—ridiculous. Look at the Bible. God clearly created the Earth around 6,000 years ago. Scientific dating methods just don’t work properly. Even if the Earth does look older, God could have designed it to look that way from the start.

Evolution was the biggest issue, and so I had the most arguments ready to debunk it. My personal favorite was “If monkeys evolved, why do we still have monkeys?”

The point is, I was ready (or so I thought) to argue with any science teacher or evolution-believing schoolmate. I was sure of what I believed. I would happily tell friends at school, “I know God is real. I know He created the world. I know we didn’t evolve.”

Actually, I didn’t know shit.

I had been handed a set of beliefs, and I never questioned them fully for myself. Why? I think it comes down to two fundamentally different ways of building our view of the world: The first is based on assumptions and the second is based on the scientific method.

Confirmation Bias, Dogma, and Common Sense

It seems like a cliché to say it these days, but it’s true: Humans are tribal beings. We naturally want to belong to a group, to receive acceptance and understanding, and to feel like we fit in somewhere. The magnetic pull to stay part of a group is incredibly strong.

This is not a bad thing. It’s something we’ve learned over thousands of years as an incredibly useful way to survive.

The lesson we learned is that together we are stronger. Alone, we’re in trouble. The bigger the group we’re in, the easier we can fight off attacks from hungry lions or other tribes, survive floods or fires, and reproduce to keep our group alive and growing.

Our beliefs and perspectives about the world have an incredible amount of power to unite and tie us closely to our tribe. It’s a great way to draw clear lines between our group and other groups. Our gods, our origin story, our holy writings, and our traditions all tell us who we are as a group and give us a stronger sense of personal identity.

This is all fine. The problem begins when we filter the evidence around us according to whether it agrees with those predefined beliefs about the world. Anything that agrees with us is friendly, true, and evidence that we’re right; anything that challenges our beliefs and gives an alternative explanation becomes the enemy. Evidence that challenges our beliefs is false and invalid; it gets ignored and discarded. This is confirmation bias, “a tendency to search for or interpret information in a way that confirms one’s preconceptions.”

As human beings, we are all affected by confirmation bias. We like to belong to communities that reinforce the things we believe, and it makes us feel more secure and confident. This is what happened as I grew up in church. The more meetings I attended, the more I was told that what I believed was right, and the more time I spent surrounded by other people who thought the exact same way.

But it’s not just religious people who are affected by confirmation bias. It’s a major part of how all our brains work, and we are all in danger of falling into this trap. In every area of our lives—whether it’s thinking about our career or our family life, our health or financial situations, our beliefs or ideas about the world—we all have to be aware of the role that confirmation bias plays. It can creep into our thinking at any time and blind us to obvious truths. It’s a sneaky bastard!

Also, not all assumed beliefs are necessarily wrong. We are all right about some things and wrong about others. By exploring ideas more carefully, we may find that some of them actually end up more well-rounded and fleshed out than before. The problem only comes when we hang onto our beliefs so tightly that we become unable to look objectively at other possibilities.

No two people within one particular group think exactly same way, after all. It’s dangerous to paint one group of people with the same brush. This is the problem with any label, whether it’s Christian, Fundamentalist, atheist, Muslim, evolutionist, Evangelical, Baptist, Hindu, agnostic, scientist, creationist, etc. Labels are an oversimplification of the complexity and variety of individual beliefs. Not all Christians think science is evil and believe in a literal six-day creation. I’m just speaking from my experience. There are a ridiculously large amount of ways to see the world, even within a single ideology like Christianity.

Dogma, as defined by the Oxford English Dictionary, means “a principle or set of principles laid down by an authority as incontrovertibly true.” There are lots of examples of dogmatic thinking in our world, but my experience mostly comes from the church. Growing up, I was taught a set of principles that explained the world I lived in. The authority for these principles was the Bible, which was described to me as an instruction manual for living (a set of Basic Instructions Before Leaving Earth) and an infallible, unchanging love letter from God.

The Bible was clear, factual, and simple. All you had to do was follow its instructions.

Our interpretation of the Bible became a set of principles set down by an authority as incontrovertibly true.

The problem with this way of thinking is that any reading of the Bible is an interpretation of an ancient writing. There are many ways of understanding the Bible, and a strictly literal interpretation is just one.

I grew up believing that the interpretation I had been handed was the only correct interpretation, and that Christians for 2,000 years had all agreed on that point. When I realized that this was only one of many ways that people had understood the Bible and that many influential Christian thinkers had even spoken against my understanding of the Bible, I had to question my perspective on everything I’d learned.

My view of the Bible slowly changed over the years from a concrete, infallible book of Truth to a more nuanced, flawed, and human collection of stories. This doesn’t take away from the value of the Bible for me; it makes it more interesting and important as part of shared history.

But as a teenage Christian, I wrote off any evidence or scientific theory that seemed to disprove something in the Bible. I had already decided the Bible was the ultimate source of all Truth. This is the very definition of dogma: Our interpretation of the Bible became a set of principles set down by an authority as incontrovertibly true.

Dogma is reinforced within tribes by confirmation bias (that sneaky bastard). We are taught to stay within safe boundaries when it comes to what we learn, read, and interact, so we fill our daily lives with things that agree with what we already believe. This is how beliefs become concrete, unchanging, and fundamental. We don’t learn anything new; we simply relearn what we already know.

Common sense can be useful in certain situations: keeping away from dangerous animals, not driving the wrong way, limiting how much ice cream we eat at one time, figuring out which bus to catch, setting our alarm to get to work on time, and so on. Common sense is a useful tool for staying safe and interacting appropriately with everyday situations. But it’s not necessarily an accurate way to make judgments about the world.

For example, imagine for a minute that you’re living thousands of years ago in this place right here:

You live all your life in a small village, on an island, separated from any other human contact. Life is hard, but simple. You fish, you eat, you sleep, you tell stories about the island monster, you make babies. You have no concept of space or planets or gravity or physics or psychology. What kinds of things could you assume about the world using only your common sense?

First, you’d probably assume the world is small. That your island is the whole world. You’ve never seen anything else, so why would you think anything else exists?

Look out at the sea. It seems to come to a sudden stop at the edge of sight. There’s a straight line there in every direction. It makes sense to assume that it’s the edge of the world.

Look up. Every morning, a bright circle of light appears, moves across the sky, and disappears again. It seems to exist just to provide you with light and warmth every day. It makes sense to assume this light is flying around your world, or being driven by some creature, or that it’s even some kind of god. It’s far away, mysterious, and magical. Without this light, you die; with it, you live and eat and grow. That sounds like something worth worshipping.

One day, a terrible storm hits your village, killing all your crops, destroying your houses, and taking the lives of many of your friends. Why would such a thing happen? It makes sense within your worldview that you’re being punished for doing something wrong. Maybe you’ve displeased the yellow god in the sky. How can you make it up to this god? Well, the same way you’d make it up to a friend or family member: with gifts and words of apology and regret.

Common sense would lead you to make many assumptions about the world. It makes total sense you would think this way, but from our perspective today, we can see that it often leads to flawed thinking and wrong conclusions.

Here’s the disturbing truth: You can find evidence to back up anything.

But it wasn’t just ancient humans who were misled by common sense.

It wasn’t that long ago when people believed our world was flat and that you’d fall off the edge if you sailed too far. The fact that we live on a huge ball flying through space went completely against common sense.

It’s only a few hundred years ago that we realized Earth was not in the center of the solar system. This was a huge deal because it took away from our sense of importance. It made our position in the cosmos seem random and unplanned. When we later learned that our solar system wasn’t even in the center of our galaxy, and then that our galaxy was just in some random corner of the larger universe, it shook our common sense even further.

Mental and physical illnesses were, for a long time, believed to be caused by demons and evil spirits. We are only beginning to learn how powerful our brains are: how they can trick us, see things that aren’t there, and invent details to make sense of unexpected events—all without us even being aware. Hundreds or thousands of years ago, with a more mystical view of the world, it would make sense to interpret strange or scary behavior as the result of dark spirits or an evil force.

Human history has repeatedly shown that common sense is a terrible way to make conclusions about how our world works.

And it all comes back to confirmation bias. Once we collect a set of assumptions, we start searching for appropriate evidence that backs up what we already believe. And here’s the disturbing truth: You can find evidence to back up anything. The best example is the internet; it’s like a giant confirmation bias machine.

You can find support for basically any belief. Does that mean all beliefs are equally valid or true? Of course not. The belief that leprechauns give birth to rainbows must be less valid than the belief in, for example, gravity.

But it raises an important question: If we are all carrying assumptions based on both dogma and common sense, and if we can find at least one other person to back up anything we want to believe, how is it possible to know anything for sure?

As much as I wish leprechauns gave birth to an explosion of magical colors across the sky, there must be some kind of line to divide beliefs that are valid from those that are best left alone.

In other words, there has to be some way to measure what is actually likely or possible or helpful in understanding how our universe really works.

This is where science comes in.

The Scientific Method

Science begins with no assumptions. There is no outside authority telling us what to think, no dogma that we can’t question, no limit to what we can explore. The key idea is this: Any hypothesis about the world must be tested and proved by repeated experiment. If you want to believe in leprechaun-born rainbows, you’d better get out in the world and observe some.

In Cosmos, astrophysicist and science writer Neil DeGrasse Tyson lays out the scientific method like this:

This adventure is made possible by generations of searchers strictly adhering to a simple set of rules: Test ideas by experiment and observation, build on those ideas that pass the test, reject the ones that fail, follow the evidence wherever it leads, and question everything.

By using this method to test every idea, we’ve learned incredible truths about the weird and wonderful ways our universe works.

For example, we’ve learned that every particle is mostly empty space, and if you somehow removed all that empty space, you could fit the entire human race into the size of a sugar cube. And time is completely relative, runs at different speeds in different places, and is not a set quantity as we might imagine.

When Galileo defended heliocentrism (the idea that the Earth revolved around the Sun instead of the other way round) he wasn’t trying to disprove the Bible or Christian belief. This theory flew in the face of ordinary common sense and certain parts of the Bible at the same time. Galileo wasn’t fighting against God; he was fighting against the easy, natural assumptions of human beings. He was asking questions and suggesting an alternative answer, which was later tested and proved.

That’s what the scientific method is about: asking questions freely, seeking evidence, and answering based on what we find. It isn’t about disproving beliefs. Science is not your enemy. It’s about discovering how the world works, through repeated testing and observation. It’s about refusing to assume something based on unfounded authority.

Religion often attracts people by selling certainty.

How do we know anything for certain? Well, we don’t. As the French philosopher Voltaire said like a complete badass: “Doubt is an uncomfortable condition, but certainty is a ridiculous one.”

Religion often attracts people by selling certainty: Yes, God created the world. Yes, you’re living a righteous life. Yes, you will go to heaven when you die.

A more healthy worldview comes with a large dose of humility: We are all human beings, with limited and treacherous brains, trying to figure out an infinite and complex universe that is way bigger than we are.

Good science embraces this idea.

Instead of giving us certainty, the scientific method works on a spectrum.

We test our ideas so that we can have an appropriate level of trust in an idea based on the amount of evidence we have to support it. The more often we see an idea work in the real world, the more confidence we can put in that idea. The more an idea helps us make accurate predictions about the world, the stronger our faith in that idea becomes. We can build up enough evidence to effectively call something true or false with a massive amount of confidence, but we also accept that we will never have 100 percent certainty.

I spent a lot of my life believing things based on “because I said so.”

Science says,Let me show you.”