Kiddush HaChodesh manifests man's influence over the spiritual process. Without man's input, there are holidays with no holiness. The Greeks believed that man is a product of nature and was controlled by it. His physical drives and lusts were an integral part of his essence, and they controlled him. Brith Mila represented Judaism conviction of man's ability to transcend his natural lusts and instincts, to control and elevate them.
Man is the unification of the physical body with an inner soul.
This uniquely Jewish concept of man having the ability to transcend his nature is represented by the number eight. One of the most frequently occurring numbers that we encounter is the number seven. It is the number of days of creation of the world, the days of the week, the days of Sukkot and Pesach, the weeks in the Omer cycle, the number of years in Shmittah and Yovel cycles, the number of days the Torah considers a woman a Niddah, the number of days required for ritual purification. It is a number very much tied to cycles in nature. It is a number very much associated with universalism as well as the totality of material creation.