Monolatrism is the belief that many gods exist but believers should worship only one. Up till the 18th Century Christians believed or generally frequently that other gods existed but that Christians should worship only one. The Merchant's Prologue and Tale suggests that Chaucer believed in the existence of the Roman god Pluto and the goddess Prosperina. As a Christian Chaucer did not worship them. Roman mosaics of the baptism of Jesus sometimes show the river god in the river Jordan. Romans believed that a river god is in every river.
The Apostle Paul in his first letter to the Corinthians writes that "an idol has no real existence" and "there is no God but one" (1 Corinthians 8:4). He argues "For although there may be so-called gods in heaven or on earth" (1 Corinthians 8:5) "yet for us there is one God" (1 Corinthians 8:6). In his second letter to the Corinthians when he refers to "the god of this world" (2 Corinthians 4:4), he is most likely referring to the devil, which as there is connection between the entity mentioned here and the "the mystery of iniquity" in 2 Thessalonians 2:7; and "the prince of the power of the air, the spirit that now worketh in the children of disobedience" in Ephesians 2:2, which are descriptions used for the devil, rather than acknowledging any separate deity apart from God. In addition, in Isaiah 44:6, God states "I am the first and the last, beside me there is no god".
As such, Christianity is normally classified as monotheism and mainstream Christian churches and denominations adhere to monotheistic doctrine as laid forth in numerous scriptural verses.
The Bible is contradictory. Some passages are best interpreted as implying that many gods exist.
In the Old Testament these sections include Exodus where the gods of the Egyptians are mentioned. Also Pharaoh’s sorcerers can turn a staff into a snake. (Exodus 7) "Thou shalt have no other gods before Me" (Exodus) 20-3 can suggest that other gods exist. Psalm 86-8 reads, “Among the gods there is none like unto thee, O Lord; (…)”. Isaiah 44-6 says, “(…) beside me there is no god".
Paul of Tarsus or whoever else wrote the epistles is contradictory. The 1st Epistle to the Corinthians suggests that there is no god but one. (1 Corinthians 8-4). Despite this (2 Corinthians 4-4) refers to the god of this world which probably means the Devil.