It is axiomatic in Judaism that Abraham was the first person to recognise that God created the world and that there are no other gods. Maimonides says as much. In the 2nd of his thirteen Principles of Faith he states that God is the First Cause. In the 5th Principle he asserts that there are no other gods beside him and it is not appropriate to worship any other entity. Abraham is the founder of Judaism. It follows that Abraham was the first monotheist, a fact known to every Jewishly educated child.
The trouble is that if we look at the bible text there is no indication that Abraham did not believe that other gods existed. It is clear that he believed in the God who created the world, but it is not at all clear that he did not believe there were other gods out there. Otherwise we would have expected him to be opposed to idolatry, and to combat it, just as the later prophets did. The people of Sodom were idolaters, but he doesn’t seem to have had a problem with that, otherwise why would he have argued with God on their behalf. When he is dragged into war and defeats the kings from the north, there is no suggestion that this a victory over their false gods, as is usually claimed elsewhere in the bible. And when Melchizedek blesses him as Priest of ‘El ‘Elyon, usually translated as Most High God, this can only mean one of two things. Either Melchizedek, not Abraham, was the first person to worship God, or ‘El ‘Elyon was another god, whose blessing Abraham is not worried about receiving.
Of course, later rabbinic literature emphasises Abraham’s monotheism, and tries to explain how he came to believe in the one and only God. There is the wonderful midrash in which a man is wandering through a forest when he sees a palace on fire. It is burning to the ground and nobody seems to be stopping it. “Surely,” the man reasons, “the palace has an owner. Why is it being left to burn?” Just then a head pops out of a window in the palace. “I am the owner of the palace” it cries. Similarly, when Abraham sees that the world seems to have no one looking after it, God reveals himself to him, declares himself to be the Master of the Universe and sends Abraham on his mission. The midrash is explaining that Abraham came to a rational, logical conclusion that God must exist.
Or the other midrash in which Abraham’s father Terah is a manufacturer of idols. One day Terah went out, leaving Abraham in charge of the store. Soon a woman came in carrying a bowl of flour. She gave it to Abraham, telling him to present it as an offering to the idols. The young man graciously took the bowl and set it down in front of the largest idol. When the woman had gone he took a hammer. He smashed every idol in the shop, with the exception of the largest, into the hand of which he placed the hammer. On his return his horrified father asked what had happened. “I can’t deceive you” replied Abraham, “A woman came with a bowl of flour. She told me to offer it up to them. This one said, “I will eat first” and another said, “No I will eat first”. While they were arguing the big one took a hammer and smashed them all.” “Do you take me for a fool?” yelled his father. “They are lumps of wood. They don’t speak and they know nothing.”
Abraham in this midrash does something that he seems to have no interest in at all in doing in the bible’s account. He mocks idol worshippers and destroys the idols.
The belief in Abraham as a monotheist seems to have evolved gradually during the second Temple period. The Book of Jubilees, probably written around 100 – 200 BCE, contains a version of the story in which Abraham smashes his father’s idols. But even in the late 1st century CE the Jewish- Roman historian Josephus can write that when there was a famine in the land of Canaan Abraham went to Egypt, to obtain food and to find out what they said about their gods. His intention was either of following them if their ideas proved better than his, or of converting them if his views were better. It seems that the process of turning Abraham into a monotheist was still pretty fluid even in Josephus’s time.
It must be the case that Abraham as not a monotheist. He taught his faith to his son Isaac who taught it in turn to his son Jacob. If monotheism, the belief in only one God was part of that faith, how come Jacob can instruct his own sons (Genesis 35,2) to throw out their ‘foreign gods’ or Rachel steal her father’s idols (31,19)? If they were monotheists, what were they doing with these things? If Abraham was a monotheist, the Bible does not seemed too concerned about letting us know.