It's not so much "against" as "lack of". You can also be "against" but it isn't necessary. It is defined by theism in the same way that "gentile" is defined by Judaism. Before Judaism, everyone was gentile, but there was no need for a word for it. "Gentile" isn't a worldview or a belief system, and neither is "atheist".
Atheists are likely to reject all "spiritual" explanations for phenomena, but the only thing that is atheist by definition is the lack of belief in deities.
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|...............| We live in the nick of times.
| Len 17, Wid 3 |
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