James Sire, whose book The Universe Next Door served as one of the primary textbooks in my worldviews class at Lincoln Christian College, offers this definition of "worldview" therein:
A worldview is a set of presuppositions (or assumptions) which we hold (consciously or subconsciously) about the basic makeup of our world.
Put simply, a "worldview" is one's view of the world. So, if "atheism" is the lack of belief in god(s), or, for some, the positive belief that there is no god(s), then can one rightly call it a worldview? The answer is: not really.
I won't even get into the question of whether atheism is a religion, because that question should be laid to rest by now. But not all worldviews are religions. So is atheism a worldview? Atheism isn't an "ism" like Buddhism or Zoroastrianism in that it's not a systemized set of doctrines or tenets (orthodoxy) or practices (orthopraxy). It's a word used to describe non-belief in god(s). Some people are "strong" atheists, in that they have the positive belief that there is no god. A strong atheist holds a godless view of the world in the same way one holds a unicornless view of the world. In that sense, atheism can be described as a worldview partially at most. It's not a "worldview" as Sire understands it: i.e., it's not "a set of presuppositions." Strong atheism only has one tenet: there is no god(s). That's it. Many other atheists (myself included), however, don't claim with positivity that no god(s) exist.
Before I go any further - and because such a reminder is needed constantly it seems - here's a chart I made today:
There are many charts like this one, illustrating the same idea. I wasn't trying to be unique. Still, it needs to be shared, because, in spite of the abundance of information on the Internet, there are people out there who still don't get it. With this attempt to clear the water a bit (or at least make it less muddy), it's better to understand "atheism" as a description of one aspect of one's worldview. In other words, "atheism" simply means one's worldview doesn't include a god or gods.
Here it's important to draw the distinction between "atheism" as a description and "atheist" as a cultural label. When someone says, "I'm an atheist," what is usually implied are things like: "I accept evolution," or "I like science," or "I value logic and reason," or "religion is bunk," among other things. None of these are necessary conditions of atheism; rather, they are commonalities shared by many who adhere to the atheist label, and there are many degrees and shades of agreement and disagreement among atheists concerning each of these. The only necessary condition of atheism is the absence of belief in god(s), and that's it.
— Dead-Logic
