Question
How do we know that G-d is One?
Answer
The unity of G-d is one of the fundamental principles of Judaism. The Biblical source for this principle is the first verse of the Shema (Deut. 6:4). The Moslems too believe that G-d is One (their profession of faith begins "There is no G-d but G-d…"), and this belief is also shared by many Christian groups who believe that Jesus was the Messiah, and was human rather than Divine.