Monotheism came from Zoroastrianism
The Babylonian captivity was a turning point in religious thought exposing the Hebrew intellectual elites to concepts which were developed in more Eastern areas, notably Zoroastrianism. Though Zoroastrianism gained the status of "state religion" in Persia only later on, the basic concepts were older (the exact date is highly disputed, but the current consensus points to "some time in the 2nd millenium BC").
The ideas had begun to percolate to neighboring Babylonia at the time the Hebrews were there. Among these concepts was the notion there was a Supreme Deity (Ahura Mazda). All other "gods" were really subordinates, even proxies; every prayer sent to any god was ultimately brought to the attention of Ahura Mazda.
When the Hebrew returned from Babylon, monotheism crystallized in their minds: they now understood that a god could be fake, non-existent. A god doesn't need a statue or a totem; if you can think about it, then it exists, and thus you can worship it.
Since monotheism was a gradual innovation, there are "intermediate states" and one cannot really pinpoint an exact year in which it happened. The term henotheism has been coined to describe these intermediaries. In the case of Europe and Middle-East, it seems that true monotheism emerged with Judaism in the 6th or 5th century BC, although some definitions of monotheism can include earlier Zoroastrianism or Atenism (as described by @Semaphore).
Well let’s go in and see what’s on display.” Katie walked into the first chamber, a square room with a statue of the ancient pharaoh displayed in a large glass box in the center of the room. It was a commanding presence. Impressed she slowly circled the statue. “I’m surprised how soft his face is.” It was a life-size bust of a man with an elongated face, full, almost feminine lips, the eyes with an oriental slant.
“Where did his oriental features come from, Neal?”
“Akhenaten’s mother Tiye was the daughter of Yuya and Tjuyu, both Syrians living in Egypt. They were probably Mitanni because they were into horses, which were still foreign to the Egyptians. Tiye’s dad, Tjuyu was put in charge of horses and cattle for the Egyptian government”
“I thought the Egyptians were already into horses, wasn’t the Battle of Kadesh a big chariot war?”
“Yeah, but this was a hundred years before. It was during this time the Egyptians came to realize the awesome power and speed horses brought to the battlefield. That’s probably why a Syrian couple living in Egypt became so important. They even fathered Ay, who became a general and a pharaoh himself.
“Akhenaten influenced art as well as religion,” Neal continued. “His artwork shows a softer side of life than previous imperial statues and reliefs have shown. He was definitely making a new statement during this time.”
Tal came in from an adjoining room. “This next room is full of tablets, almost like a library.”
“Here is the Amarna Room,” Neal said. “These are the clay tablets Akhenaten used to correspond with the other kings and government officials throughout the ancient world.”
“How big was his world? How many people could he have written to?”
“Well Katie, the clay tablets, there are more than three hundred of them, indicate some of his correspondents was from empire called the Hittites, in what is now modern day Turkey. They became increasingly assertive during Akhenaten’s rule, going to war against the Mitanni beneath them in Syria and Iraq, who were an Egyptian ally. In addition to their conflicts with the Mitanni, the Hittites were also stirring up instability in the vassal states of Syria, and helping a Semitic nomadic group, the Apiru, to create unrest in Syria-Palestine.”
“All of this was going on three thousand years ago?”
“Yes, about then. And the Old Testament deals with a lot of this stuff too. The information we get from the tablets is corroborated in the Bible.”
Katie was fascinated. This stuff intrigued her to no end, but when she looked at Tal, she could tell he wasn’t at all enthralled.
“What else did you find in the other rooms, Tal?”
“Just more stone stuff. I was hoping for mummies and chariots and lots of gold.”
Amenhotep III and Queen Tiye
Akhenaten and his family lived in the great religious center of Thebes, city of the God Amun. There were thousands of priests who served the Gods. Religion was the business of the time, many earning their living connected to the worship of the gods.
All indications are that as a child Akhenaten was a family outcast. Scientists are studying the fact that Akhenaten suffered from a disease called Marfan Syndrome, a genetic defect that damages the body's connective tissue. Symptoms include, short torso, long head, neck, arms, hand and feet, pronounced collarbones, pot belly, heavy thighs, and poor muscle tone. Those who inherit it are often unusually tall and are likely to have weakened aortas that can rupture. They can die at an early age. If Akhnaton had the disease each of his daughters had a 50-50 change of inheriting it. That is why his daughters are shown with similar symptoms.
Akhenaten was the son of Amenhotep III and Queen Tiyee, a descendent of a Hebrew tribe. The largest statue in the Cairo Museum shows Amenhotep III and his family. He and Queen Tiye (pronounced 'Tee') had four daughters and two sons. Akhenaten's brother, Tutmoses was later named high priest of Memphis. The other son, Amenhotep IV (Later to take the name Akhenaten) seemed to be ignored by the rest of the family. He never appeared in any portraits and was never taken to public events. He received no honors. It was as if the God Amun had excluded him. He was rejected by the world for some unknown reason. He was never shown with his family nor mentioned on monuments. Yet his mother favored him.
A replica of the Tuthmoses IV Sphinx Stele.
The Sphinx was seen by ancient Egyptians as a representation of an ancient aspect of the sun god, Horemakhet, which means Horus in the Horizon. On this stele Tuthmose IV makes it clear that he owes his throne to the intercession of Horemakhet and no mention is made of Amun. In part the stele reads;
“Look at me, observe me, my son Thutmose. I am your father Horemakhet-Khepri-Ra-Atum. I shall give to you the kingship [upon the land before the living]….[Behold, my condition is like one in illness], all [my limbs being ruined]. The sand of the desert, upon which I used to be, (now) confronts me; and it is in order to cause that you do what is in my heart that I have waited.” (Stele of Tuthmose IV)
Solar Court at Karnak.
Even though the new pharaoh claimed to be a son of Amun the Amun priesthood was so to be diminished. Within the first decades of Amenhotep’s reign members of the Amun priesthood had lost the rights to several powerful posts such as “overseer of all priests of Upper and Lower Egypt” and Amenhotep’s own loyal appointee, Ptahmose, was “First Prophet” (high priest) of Amun. This effectively gave the crown the control over the cult of Amun’s hierarchy. However even with the loss of political power by the Amun priesthood the city of Thebes had become the cosmological center of the Egyptian universe and so the power of its god endured.
It was perhaps the rise of a powerful family in Egypt that eventually caused Atenism to approach its final phase. The importance of this family is witnessed by scarabs produced during the reign of Amenhotep III where his wife Tiye and her parents Yuya and Tuya are mentioned. These scarabs, along with Yuya and Tuya’s tomb being found in the prestigious location of the Valley of the Kings, indicates individuals who held exceptional influence at the royal court. The significance of Yuya’s influence spurs from the possibility that he was of foreign origin and may have sponsored the idea of a universal sun-god which had broad appeal in the Near East at this time. Together with other foreign notables who would come to power, such as the Vizier Aper-el, immigrants, who settled in the north of Egypt, began to hold considerable influence in the administration.
Whether or not he was influenced by foreign ideas is ultimately uncertain, yet Amenhotep III surely embarked on a course of religious reform that reshaped the final decades of the 18th Dynasty. Since the most ancient pharaohs had ruled as gods rather than just becoming a god upon death a move to restore this practice could be seen as a conservative move by the tradition bound Egyptians and it was in this guise that the religious changes took place.
When Amenhotep III built a temple in Nubia he ensconced himself as the solar god and Queen Tiye was worshiped as the solar god’s consort, Hathor. Buried in the courtyard of Luxur temple where he inscribed scenes of his divine birth as a son of Amun a statue of Amenhotep III was discovered portraying him in full solar regalia as the rejuvenated sun god.
The Rise of the Aten
When Amenhotep III built his famous palace across the river from Thebes he named it “House of Nebmaatre – splendor of Aten”. The military’s crack unit was named after the Aten as was the navy’s flagship. In spectacular fashion when a visitor approached the pharaoh’s massive mortuary temple the colossal statues known today as the Colossi of Memnon, were said to cast their own light which would “fall on the face like Aten when he shines at dawn.”
Even with this increased status of the Aten the pharaoh was careful to include all the well-known deities in such works as his mortuary temple which contained an unknown number of divine statues. It was near the end of Amenhotep III’s reign when the new royal Aten cult really began to take control. In his thirtieth year the pharaoh celebrated his heb-sed (jubilee) festival, which traditionally saw the pharaoh symbolically rejuvenated, Amenhotep III instead transformed himself into the deity, Aten the Dazzling Sun Disc; a living god.
After this transformation inscriptions of the pharaoh show the familiar shebyu-collar and gold armbands. However a new threshold is crossed when the pharaoh changed the way his throne name, Nebmaatre (possessor of the truth of the sun god), was written. For the final years of his reign the hieroglyphic inscription of Amenhotep III’s throne name was shown occupying the sun’s place in the magical barque which traveled across the sky each day.
Akhenaten and family with the Aten.
When Akhenaten succeeded to his father’s throne it was with the name Amenhotep IV and like his father he gave all the early signs that he would keep up the charade with the priesthood of Amun. Then something (what exactly is open to debate) changed and the new pharaoh decided he had to make a clean break with tradition. So clean in fact that a new capital had to be constructed on ground that had never before been consecrated to any god. Here he ordered a new city be built. It was to be Akhetaten, “Horizon of the Aten” replete with several palace compounds and massive solar temples it was to become the new capital of the empire. Today the ruins of this city are known as Amarna.
Wealth previously directed to temple cult’s throughout the realm was then directed to the new city. Although contrary to common belief all of the other temples were not simply shut down. However a particular focus was made to literally carve out the influence of the god Amun. For over a decade all the wealth of Egypt was focused on making this new religious transformation work. Then with the death of Akhenaten the Aten movement unraveled. The new pharaoh was named Tutankhaten, literally “living image of the Aten” however within a few years the newly built capital was abandoned, the wealth and influence of the Amun priesthood was restored and the pharaoh changed his name to Tutankhamun just to be safe.
Aten is the disk of the sun in ancient Egyptian mythology, and originally an aspect of the god Ra. The deified Aten is the focus of the religion of Atenism established by Akhenaten in worship and recognition of Aten. In his poem "Great Hymn to the Aten", Akhenaten praises Aten as the creator, giver of life, and nurturing spirit of the world.
Prior to Amenhotep IV, the sun disk could be a symbol in which major gods appear and so we find such phrases as "Atum who is in his disk ('aten'). However, from there it is only a small leap for the disk itself to become a god.
Aten is known as the sun disk god. He was first introduced in the Middle Kingdom as a characteristic of the sun god Re. He was consider a separate god for the first time under Tuthmosis IV. Under Tutmosis son Amenhotep III, a cult was formed to worship Aten.
Though the Aten became particularly important during the New Kingdom reigns of Tuthmosis IV and Amenhotep III, mostly sole credit for the actual origin of the deity Aten must be credited to Amenhotep IV (Akhenaten). Even at the beginning of the New Kingdom, it's founder, Ahmose, is flattered on a stela by being likened to "Aten when he shines". His successor, Amenhotep I, becomes in death "united with Aten, coalescing with the one from whom he had come". Tuthmosis I was portrayed in his temple at Tombos in Nubia wearing the sun disk and followed by the hieroglyphic sign for 'god'. Hatshepsut used the term on her standing obelisk in the temple of Karnak to denote the astronomical concept of the disk, though it was actually during the reign of Amenhotep II that the earliest iconography of Aten appears on a monument at Giza as a winged sun disk (though this was a manifestation of Re) with outstretched arms grasping the cartouche of the pharaoh.
With the reign of Amenhotep IV, whom we know more familiarly as Akhenaten, the worship of Aten came to its pinnacle. Amenhotep IV started his reign in the capitol city of Thebes. He had difficulties with the powerful priesthood of Amen-Re which had its main temple at Karnak. In the fifth year of his reign, he disbanded the priesthood of all the other gods in Egypt except Aten. He changed the religion from polytheistic to monotheistic. The King changed his name to Akenaten, meaning "servant of Aten." In addition, he moved the capitol city from Thebes to a newly constructed city of Akhetaten.
Ra-Horakhty is a combined deity of Horus and Ra, and is usually depicted as a falcon-headed man wearing a sun disk on his head.
It was Amenhotep IV who first initiated the appearance of the true god, Aten, by formulating a didactic name for him. Hence, in the early years of Amenhotep IV's reign, the sun god Re-Horakhty, traditionally depicted with a hawk's head, became identical to Aten, who was now worshipped as a god, rather than as an object associated with the sun god. Hence, prior to Akhenaten, we speak of The Aten, while afterwards it is the god Aten. Initially, Aten's relationship with other gods was very complex and it should even be mentioned that some Egyptologists have suggested that Amenhotep IV may have equated Aten to his own father, Amenhotep III. Others have suggested that, rather than true monotheism, the cult of Aten was a form of henotheism, in which one god was effectively elevated above many others, though this certainly does not seem to be the case later during the Amarna period.
The ancient Egyptian term for the disk of the sun was Aten, which is first evidenced during the Middle Kingdom, though of course solar worship begins much earlier in Egyptian history. It should be noted however that this term initially could be applied to any disk, including even the surface of a mirror or the moon. The term was used in the Coffin Texts to denote the sun disk, but in the 'Story of Sinuhe' dating from the Middle Kingdom, the word is used with the determinative for god (Papyrus Berlin 10499). In that story, Amenemhat I is described as soaring into the sky and uniting with Aten his creator.
Text written during the New Kingdom's 18th Dynasty frequently use the term to mean "throne" or "place" of the sun god. The word Aten was written using the hieroglyphic sign for "god" because the Egyptians tended to personify certain expressions. Eventually, the Aten was conceived as a direct manifestation of the sun god.
During the reign of Amenhotep III, there is evidence for a priesthood of Aten at Heliopolis, which was the traditional center for the worship of the sun god Re, and he also incorporated references to the Aten in the names he gave to his palace at Malkata (known as 'splendor of Aten'), a division of his army and even to a pleasure boat called 'Aten glitters'. Also, several officials of his reign bore titles connecting them with the Aten cult, such as Hatiay, who was 'scribe of the two granaries of the Temple of Aten in Memphis. and a certain Ramose (not the vizier) who was 'steward of the mansion of the Aten'. The latter was even depicted with his wife going to view the sun disk.
Egypt received vast wealth not only in terms of gifts sent by other countries but also as booty brought back from military campaigns. Much of this booty was presented to the God Amen-Re and his priesthood in the temple of Karnak at Thebes because the early rulers of Dynasty 18 credited their military success to Amen-Re as their patron deity. Consequently this temple and its priesthood became so wealthy and powerful that, by the end of the Dynasty 18, the priests posed a considerable political threat tot he royal line.
Amun is described as the primeval creator in the Pyramid Texts which depict him as a primeval deity and a symbol of creative force. However, he rose to prominence during the Eleventh dynasty when he replaced the Theban war god, Montu, as the principle deity of the city. From that point, the fortunes of the God were closely linked to the prominence of Thebes itself. When the Theban Ahmose I successfully expelled the Hyksos from Egypt, he was quick to show his gratitude to Amun and throughout the Middle Kingdom the Royal family established temples to Amun, most notably the Luxor Temple and the Great Temple at Karnak.
During the New Kingdom he gained such power that it is almost possible to argue that Egypt had become a monotheistic state. Amun-Ra was considered to be the father and protector of the pharaoh. The Theban royal women wielded great power, and influence and were closely involved with the cult of Amun. Queen Ahmose Nefertari (the Great Wife of the Pharaoh Ahmose I) was granted the title "God's Wife of Amun" with reference to the myth that Amun created the world by masturbation. This title was then granted to the Great Wife of every Pharaoh in recognition of her role in the state religion of Amun. The female Pharaoh Hatshepsut went one stage further and specifically stated that Amun had impregnated her mother (in the guise of the Pharaoh Thuthmoses II, her father). Thus she established her right to rule on the basis that she was his daughter.
However, the god could also reveal his will through the oracles, who were in the control of the priests and they had been granted so much land that they even rivalled the power of the Pharaoh. Amenhotep III instituted some reforms when he became concerned that the Theban clergy had become too powerful, but his son (Akhenaten) went one further and actually replaced Amun with the Atenand constructed a new capital city named Akhetaten. However, the experiment was short-lived and both Amen and Thebes were reinstated under the rule of Tutankhamun.
Amon-Re was originally known just as Amon, Amen or Amun. In Thebes, where Amon was considered their patron saint, he was merged with Re, the sun god. Amon-Re was associated with creating the world and protecting the helpless. In Hermopolis, worshippers of Amon-Re believed that he married Mut and had a son named Khonsu, the god of the moon. The worship of Amon-Re survived many periods of Egyptian history.