Back in the 1960s, when I was in primary school in Drumcondra in Dublin, we were given a project to do over the Easter holiday. We had to read the Gospels, and rewrite them in our own words. I spent ages doing this, rewriting the stories and drawing pictures to accompany them.

Midway through doing this, it dawned on me that none of this ever happened. These were comic-book stories about a comic-book character, a superhero who could do magic. From then on, I didn’t believe in gods.

My parents were cultural Catholics from Tipperary and Clare. They often went to Mass, but always told me that I should make up my own mind about religion when I was old enough. While I didn’t believe in gods, I was fascinated by the big questions that religion claimed to have the answers to. How did the universe come to be? What is the meaning of life? How should we live together?

The religious answers seemed flawed, particularly as I learned more about the scale of the universe and how life on Earth evolved. Why would a supreme being create such a vast universe for just one of millions of species living on just one of billions of planets? Why would such a supreme being care about what we did in our bedrooms, or what we chanted on Sundays? Why would he give different messages to different people in different places at different times?

And yet for years I described myself as an agnostic rather than an atheist. Saying for certain that there was no God just seemed to be a step too far, as nobody could prove one way or another whether or not it was true. And so I started to believe in the analogy of the three blind men and the elephant.

One blind man touches the elephant’s trunk and says, “The elephant is like a hosepipe.” Another blind man touches the elephant’s leg and says, “No, the elephant is like a tree trunk.” And the third blind man touches the elephant’s tail and says, “No, you’re both wrong; the elephant is like a piece of rope.” In the same way, I believed there was a universal reality and that all religions had a limited glimpse of some of it.

That grated with me, because it seemed to suggest all religions were equally true, though equally flawed. But it also seemed almost infinitely more likely that there were no gods than that there were gods. And yet I could not, with 100 percent certainty, discount the possibility. The dilemma seemed irresolvable, until I realised that I was applying different standards to my beliefs about gods than to my beliefs about anything else.

Strictly speaking, we cannot be certain about anything, even that we exist. What appears to be consciousness might be an illusion, and reality may be nothing like it appears. And so, in order to function sanely, we assume that reality is broadly as it appears, based on applying reason to the apparent evidence of our senses. And the best way to test this is the scientific method: make an educated guess, conduct unbiased experiments to see how that guess matches up to the evidence, and then reject or refine your idea based on the outcome of the experiments.

When we do that, we realise there is no need to invent gods in order to explain either reality or morality. Every generation, the scientific method teaches us more about how the universe operates. Every generation, religious people describe the bits that we don’t yet understand by saying that “God did that.” Every generation, we patiently move more and more answers from the “God did that” category into the “we now understand how it happens naturally” category. And we never move any answers in the opposite direction.

Crucially, the scientific method never claims to be 100 percent certain about anything. All it says is that, based on the best currently available evidence, this is what seems to be the case so reliably that, in practical day-to-day terms, we describe it as being true beyond reasonable doubt. However, if we ever get any new evidence that shows that we are mistaken, then we accept that we were mistaken and revise our ideas to match the new evidence.

If we apply the same reasoning to the question of whether gods exist, we can reliably say they do not exist based on the best currently available evidence. This is not a claim of certainty, and it is open to change based on new evidence, but it is a reasonable response to the best currently available evidence, and to centuries of related evidence. There is no good evidence that gods do exist, and lots of good evidence that the idea of gods was invented by human beings. It was realising this that enabled me to feel comfortable describing myself primarily as an atheist rather than an agnostic.

Atheism is also a better basis for investigating morality. Right and wrong are ultimately about how we affect the suffering and wellbeing of other sentient beings. Helping other sentient beings to flourish is good, and causing other sentient beings to suffer unnecessarily is bad. It is complicated to figure out what is right and wrong in any given situation, because there are so many permutations of the effects of your actions.

However, religion distracts us from identifying what is right and wrong by adding in answers that are unrelated to suffering and wellbeing in the real world, but are based on imaginary souls and imaginary consequences in imaginary afterlives. And so you get contradictory messages in books like the bible, which tell us to love our neighbour but stone him to death for gathering sticks on the Sabbath. We know that this last command is morally wrong, and so we ignore it. This shows that we do not get morality from the bible, but apply our morality to what we read in it.

But aside from the science and theology, it was the behaviour of many religious people that caused me to become an atheist activist. Not all religious people, of course, but many of those that have influence. The Catholic Church has influenced many Irish laws, and has a widespread culture of covering up the sexual abuse of children by priests. Islamic states infringe on the human rights of their citizens, and Islamic extremists fly airplanes into buildings.

And so I helped to found Atheist Ireland, an advocacy group that promotes atheism and reason over superstition and supernaturalism, and that lobbies for a secular state that shows no favour to any religious belief. We want a secular Irish constitution, a secular education system and an end to the many links between church and state in Ireland. Everyone has a right to believe what they want about the supernatural, but the state should be strictly neutral about this.

This article was first published in September in The Hibernia Times.