Thanks. Religion is typically equated with theism, but religion is better regarded in more neutral, sociological terms which enable us to speak of a civic religion or of an atheistic one such as Buddhism or perhaps consumerism. But that can get confusing, so it depends on the context for me.
I've written a number of articles on mysticism, and I even had a long written debate about the difference between mystical and secular forms of enlightenment. My pragmatic view of knowledge entails that our knowledge will always be incomplete because of the subjective, cultural component, which is subject to change.
The argument in this article, though, is specifically in support of atheism, which means it's opposed to theism. Mysticism needn't be theistic, so that's sort of a side issue.