Over half the world practices Christianity, Islam or Judaism, according to Pew Research Center. These religions are all monotheistic, involving the worship of one God. But according to scholars, our modern understanding of monotheism is a recent phenomenon — more recent even than the religions it describes.
So, how did monotheism emerge?
The answer is complicated. Monotheism didn't emerge with Judaism, nor Christianity, nor Islam, according to scholars. It's a modern concept. And depending on how you define it, it either emerged thousands of years before these major religions, or hundreds of years later.
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At a surface level, many ancient religions look polytheistic. Whether you're looking at Mesopotamia or ancient Egypt, Greece or Rome, the Kingdom of Aksum in northern Africa or ancient Israel: all of these civilizations once worshipped many gods. The reality is a little more complicated, said Andrew Durdin, a religious historian at Florida State University.
"When you look across human history, the distinction between polytheism and monotheism kind of falls apart," Durdin told Live Science.
Across cultures, pantheons, or groups of deities specific to a particular religion, were often written about as expressions of the same divine entity, similar to how Christians worship the Holy Trinity — the father, the son and the holy spirit — as different manifestations of God. For example, in the second millennium B.C., the ancient Mesopotamian epic poem, "Enuma Elish," calls the chief god Marduk by 50 names: the names of those gods subordinate to him. The implication is that these lower gods were really manifestations of one god: Marduk, wrote Jan Assman in the book "Religions of the Ancient World: A Guide" (Belknap Press of Harvard University Press, 2004).
This concept of divine unity wasn’t unique to Mesopotamia; this same concept existed in ancient Greece, Egypt and Rome. In ancient Rome around the third century B.C., a philosophical group called the Stoics maintained that there was only one God, whose names only differed according to his or her role in the heavens and on Earth, Assman wrote. Increasing connectivity between civilizations may have encouraged the belief in divine unity, Assman wrote. People drew connections between their own gods and those of other societies. They began to see different gods and pantheons not in opposition to one another, but as expressions of the same concept. Some scholars compare the idea of divine unity to monotheism. Assman calls it "evolutionary monotheism"; Durdin calls it "philosophical monotheism." However, not all scholars of religion agree with this interpretation.
Put another way, ancient people may have viewed multiple gods from different cultures as all emanating from the same holy source.
It was in this context that religious movements began demanding exclusive worship of one God. In the 14th century B.C., the Egyptian pharaoh Akhenaten established a cult devoted only to the sun god, Aton. He closed temples and destroyed images of other gods. And some scholars believe it was up to a thousand years later that early Israelites began worshipping only one god: Yahweh, said Matthew Chalmers, a theorist of religion at Northwestern University in Illinois. It was a transition that took centuries, and it would be centuries more before the belief that only one God exists became cemented in Judaism, Chalmers said.
It's important to note that these people didn't think of themselves as monotheists or polytheists. "I don't think it was something ancient people were really interested in," Chalmers told Live Science. These movements didn't deny the existence of other gods. They just demanded that people stop worshipping them.
Similarly, early Christians didn't explicitly declare other gods nonexistent; they began referring to them as demons, Chalmers said. Proclamations that there was only one God show up in portions of the Hebrew Bible written around the fifth century B.C. — however, sections written earlier in Jewish history made no such claims, Chalmers said. And it wasn’t until the third and fourth centuries A.D., that the concept of one God finally began appearing in Christian liturgy. However, scholars disagree on the exact timeline, he added. Islam was slightly a different story. The Quran, which was penned within decades of Islam's emergence in the seventh century, explicitly stated that there was only one God from the get-go, said Chad Haines, a historian of religion at Arizona State University. That doesn’t mean that monotheism emerged with Islam, however — this was a development that built on earlier religious traditions and continued to evolve over time.
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So what was so significant about these periods in history, when religions began out-right declaring that there was only one God? It's impossible to elucidate cause-and-effect. But there were a few significant changes. More people were writing down their ideas, especially elites, Chalmers said. Owning a religious text became a mark of social status. And states began throwing themselves behind specific religious movements. For example, in Rome's later days, the idea of one God appealed to emperor Constantine as a way to pull together the crumbling empire, Durdin said.
Still, it wasn't until 1660 that the term monotheism was first used, and decades later the term polytheism, Chalmers said. Later, the distinction was made as a way to help explain why some societies were "civilized" and others were "primitive."
"I don't think there is a transition to monotheism," Chalmers said. After all, not everyone even agrees that Christianity, the largest ostensible monotheistic religion, is monotheistic at all, he added — some Jewish and Muslim writers interpreted the Holy Trinity as three gods rather than one. Instead, the distinction between polytheism and monotheism is one we've made in retrospect to try and make sense of our own history.
"It's a modern imposition," Haines said, "It allows us to map monotheism as a move towards progress."
Originally published on Live Science.