Atheism is the simple but kind of startling idea that no god or gods exist. If you’re interested in exploring the topic, it helps to know some of the labels for different types and degrees of religious doubt, some of the most important thinkers in the history of atheism, and a few of the most fascinating spots on Earth for just saying no to God.

A lot of people think that atheism is a recent idea. But religious disbelief actually has a long and fascinating history. Just as a student of Christianity would want to know about a few rather significant things that happened 2,000 years ago, someone who wants a better understanding of atheism likewise needs to know what atheism has been up to for the past 30 centuries or so.

Most religious believers want to live in a world in which people behave ethically. Funny thing…so do most atheists. An ethical society is simply safer, less scary, easier, more satisfying to live in, and simply better, whether or not a person believes in God. That’s the kind of place everyone want their kids to live in.

Atheism is a big umbrella. There are about as many ways to disbelieve as there are ways to believe — different degrees, different emphases, and different expressions. It covers anyone who doesn’t believe in a supernatural god or gods. But under that umbrella are many shades and grades of disbelief and many people with different ways of approaching and expressing it.

No matter what your perspective, the idea of religious atheism is probably a head-spinner at first. If someone said “religion,” the odds are pretty good that “God” is one of the first related words to pop into your head. Religion and God have been joined at the hip from the beginning. In fact, a person can be an atheist who also considers him or herself religious.

Atheism, humanism, and all the rest of the nontheistic isms show up in different ways around the world. What follows is a list of some of the most interesting places to watch for developments in religious disbelief. Earth: Current home to 1.1 billion nontheistic people. Ireland: Where those who call themselves “religious” dropped from 69 percent to 47 percent in seven years — the largest drop on Earth.

Atheism and other kinds of religious doubt are chock-a-block with labels and terms. Some are more important than others; some are neutral or positive; others are used (even by atheists) as putdowns. The following list includes all of the major labels — good, bad, and ugly. Atheist: Doesn’t believe a god or gods exist.

The history of atheism is filled with important figures — people who have thought outside of the religious box of their times and often used their eloquence and intellect to convince other to do so as well. Some have also distinguished themselves as moral or intellectual heroes in the great issues of their day.

Science fiction writer Isaac Asimov calls the Bible “the most potent force for atheism ever conceived” — and many atheists agree. But most people are only familiar with that carefully handpicked sampler of inspiring passages from the Bible. For each and every inspirational passage that finds its way into pulpits and needlepoint pillows, half a dozen immoral horrors stay pretty well hidden.