Critics of atheism sometimes assert that atheism is a religion. Given that the critics nearly always are themselves religious, it is strange that the assertion tends to emerge from their mouths in the form of an accusation, as though they believe they have uncovered some scandalous crime. But never mind the peculiarity of the rhetoric; it is a legitimate question, which admits of a dispassionate answer: is atheism a religion?
The answer is no, atheism is not a religion. Atheism is not comprehensive enough to be a religion. Atheists have no credo, no priesthood, no holy books, no objects of worship—none of the things that normally are associated with religions. To call atheism a religion when it lacks such things, is to stretch the word religion to the point of vacuity. Likewise, the predictable responses that university professors are the atheist priesthood, that On the Origin of Species is the atheist holy book, that atheists worship themselves, and similar such nonsense, are no more than crude (though convenient) equivocations on the terms priesthood, holy book, and worship. One might as well assert that the term child abuse means god, and then argue on that basis that all believers love child abuse.
Atheism can, of course, be incorporated into various secular ideologies, some of which are sufficiently cultish to bear analogy to religion—certain strains of Marxism, for instance, being the most commonly cited example—and it is possible to find minor atheistic schools in some of the major world religions, which perhaps retain enough of their ancestry to continue to qualify as religions. However, this does not mean that atheism is itself a religion, or that any particular atheist must accept any of the ideologies or schools above. Just as belief in an immaterial soul can be a component of a religion, but is not itself a religion, so with atheism. Even in the context of a cultish worldview that incorporates atheism, atheism is no more a religion than a library book is a library, an atom of hydrogen is a water molecule, or a cup of flour is a chocolate cake.
In the end, calling atheism a religion is akin to calling capitalism, or pacifism, or too much time in front of the television, a religion—it is just a way certain people have of pointing at something they don’t like, and implying that everyone associated with that something is a fanatic. In short, the claim is mere rhetoric, after all. In the normal sense of what it takes for something to be a religion, atheism doesn’t qualify.