In the study of religions, you will come across terms and ideas that avail themselves to many different interpretations. You saw this when looking at theism. It’s not always clear which religions might fit best into this category.
This is true for non-religious beliefs. The belief that there is no God is a non-theistic belief. Atheism is a committed position ascribing to the belief that God doesn’t exist. It can securely be put under non-theism.
Another more formal method of thinking about religious beliefs is religious skepticism. This might be harder to group clearly into one camp or another, theism or non-theism. A religious skeptic would like to subject certain religious beliefs to rational scrutiny, perhaps even his or her own beliefs. So, he or she might be a believer, a faithful adherent of one religion or another.
When it comes to specific religions themselves, there are many that don’t honor or worship a particular deity. Confucianism, Taoism, and many schools of Buddhism are good examples of non-theistic thought, non-theistic religions. They generally fit more clearly into non-theism.
Although it doesn’t have a god who is worshipped in the way a Hindu god is revered and worshipped, Buddhism’s founding principles are nevertheless related to ideas of the non-material and ideas of the sacred. In other words, its focus is on consciousness and the spiritual life that allows for integration of matter and spirit and the possibility of transcendence. For this reason, Buddhism has historically been approached and interpreted from a variety of angles.
Source: This work is adapted from Sophia author Ted Fairchild.