Buddhism is an atheist religion because in the creation narrative of Buddhism, the samsaric cycle that is responsible for the cosmos was not created by god(s), nor is it ran by gods. Everything is subservient to this without-gods (a-theos - atheist) system. Nearly all classical Buddhist scholars assert that Buddhism is atheistic1,2,3,4,5,6,7,8,9,10,11. Nonetheless, Buddhist texts often talk of gods (just as the Old Testament does) although they are not the same kind of eternal being that Westerners would expect - the cause of this is that there are no easy words to describe the nature of some of the powerful beings that inhabit Buddhist stories without using the word "gods". Despite the appearance of such beings, however, it is certainly untrue to say that Buddhism is formally theistic, therefore, it is best described as atheistic.
Christmas Humphreys was President of the Buddhist Society, London, from its foundation in 1924 until its Silver Jubilee in 1954. In his book Buddhism12 he writes "as between the theist and atheist positions, Buddhism is atheist"1.
In a prominent book by one of the founders of academic religious studies, "The Varieties of Religious Experience" by William James (1902) [Book Review]13, James says "there are systems of thought which the world usually calls religious, and yet which do not positively assume a God. Buddhism is in this case. Popularly, of course, the Buddha himself stands in place of a God; but in strictness the Buddhistic system is atheistic"2.
Tanebaum, Center for Interreligious Understanding, publish statistics on world religions and note that Buddhists can sometimes be double-counted because they are included as "religious" and "atheist"15. This only happens, of course, when we fail to realize that "non-religious" means non-religious, and "atheist" does not mean non-religious. So if you add "atheists" to "religious" stats, you will end up double-counting Buddhists.
André Droogers' essay Defining Religion: A Social Science Approach warns that too many definitions of religion are exclusively monotheistic and says that this causes a "problem" - if religion is defined purely in terms of theism "some forms of Buddhism would have to be excluded"6.
The Penguin Dictionary of Religions18' entry on Buddhism points out that in all of reality Buddhas are "reckoned to be its highest beings [but they] are not conceived of as omnipotent creators of the universe"7.
"Contrary to what many Westerners think, traditional Buddhists do not worship Buddha as a god. Siddhartha Gautama, the Buddha, never claimed to be a god. Therefore, most Buddhists are atheists" -- Guy Harrison in "50 Reasons People Give for Believing in a God" (2008)8.
Stephen Batchelor, a lifelong Buddhist and a Buddhist monk for 13 years from 1972 to 1985, still teaches and talks on Buddhism. He says "when someone asks me if I believe in God, I have to answer that I have no idea what the question means... the Buddha likewise, and his followers, have never had use, or need for, a word which would be equivalent to the English word, God".9
Scholar of comparative religion, Moojan Momen, explains:
“In contrast [to Western theism], the Eastern religions, Buddhism [has] no concept of God as a person; rather their concept is of Ultimate Reality as a process, a truth, or a state of being [which is] both transcendent and imminent. It cannot be described in terms of the concepts of this phenomenal world. It is devoid of all empirical determinations. It is not an all-knowing Creator.”
Religion is complicated, and there is often a discrepancy between what the cultural followers of a religion do, and what the religion formally asserts. In "Cultural Religion Versus Scholarly Religion" by Vexen Crabtree (2013) I explain how it is normal for a religion to be officially one thing, but for the grassroots masses to have a variety of cultural beliefs and practices, sometimes making it hard to clearly define what a religion is. It happens that Buddhist texts often mention gods, and, some Buddhists themselves often worship various gods8.
In "The Phenomenon Of Religion: A Thematic Approach" by Moojan Momen (1999)20 the worship of deities is said to have continued in many forms of Buddhism despite Western scholars thinking that, because of their texts, Buddhism was atheist21. Note that Momen is a Bahá'í who therefore believes in a certain unity of all religions under a single god, therefore he comes from a slightly biased position.
In Zen Buddhism no assumptions are made about any mind that might be responsible for ultimate reality. It is unclear whether or not ultimate realty should be described as being ruled by an intelligent being or not:
“This mysterious Mind... is higher than the highest, deeper than the deepest, limitless in all directions. There is no centre in it. No distinction of east and west, and above and below. Is it empty? Yes, but not empty like space. Has it a form? Yes, but has no form dependent on another for its existence. Is it intelligent? Yes, but not intelligent like your mind. Is it non-intelligent? Yes, but not non-intelligent like trees and stone.”
Some academics find themselves in a strange situation of denying that Buddhism is a religion at all; Malcolm Hamilton says that "the atheism of canonical Theraveda Buddhism" makes that official form of Buddhism a non-religious thing, compared to a more popular kind "that postulates the existence of various supernatural beings [so is] considered, therefore, to be truly religious"23. By his definition, supernaturalism defines religion, but he still cannot come to call Theraveda Buddhism "religious" because it doesn't contain supernatural gods; hence it is "atheistic" and "non-religious". The inconsistency is resolved by using the words properly: "atheist" means "without gods", and "non-religious" means "without religion".