Moses said to God, "Suppose I go to the Israelites and say to them, 'The God of your fathers has sent me to you,' and they ask me, 'What is his name?' Then what shall I tell them?" God said to Moses, "i am who i am. This is what you are to say to the Israelites: 'i am has sent me to you.'"
Hear, O Israel: The lord our God, the lord is one. Love the lord your God with all your heart and with all your soul and with all your strength.
The wrath of God is being revealed from heaven against all the godlessness and wickedness of people, who suppress the truth by their wickedness, since what may be known about God is plain to them, because God has made it plain to them. For since the creation of the world God's invisible qualities—his eternal power and divine nature—have been clearly seen, being understood from what has been made, so that people are without excuse.
In the process of learning acceptable mathematical procedures for writing an argument which is convincing to other readers, we study predicate logic. Determining what portion of the entire collection will satisfy a relationship is one component of the argument. Mathematicians indicate the special cases of all, at least one, and exactly one with quantifier notation. If an open statement P(x) is true for all valid replacements x, we write "x,P(x). If the open statement P(x) is true for at least one replacement, we write $x,P(x). And, if an open statement is true for one and only one replacement, we write $!x,P(x). Unique existence of a valid replacement is one of the most special cases to consider. A proof of this type of statement always requires two parts: first, you must show that at least one solution exists (i.e., existence of solution); then you must show that not more than one solution exists (i.e., uniqueness of solution).
Abraham and his descendants were chosen to be the first people on earth to be led to comprehend both aspects of the unique existence of God. One instance of the existence portion of God is found in the story of Moses meeting God in the burning bush. Here, God reveals his name to Moses as evidence that He truly exists. God says, "I am who I am." [Note: Exodus 3:13--14. I especially enjoy the transcendence of God to time given within the Hebrew for this phrase--the phrase can be interpreted with past, present, and future verb tenses!]
Later, at Mount Sinai, Moses is given laws to train the infant-nation of Israel in the ways of God. In Deuteronomy 6:4, Moses recounts the uniqueness condition told him by God: "Hear, O Israel: The Lord our God, the Lord is one." Even though both aspects of the "$! God" were provided to Israel from the time of the exodus, we know from Old Testament stories that the lesson was a difficult one for these chosen people to learn. I think even today we struggle with acknowledging God's unique existence, though few Christians will deny the truth of the statement.