A friend asked the other day why we have a Bris (circumcision). I rambled on about health, tradition, old people, 8 days, pain and a whole lot of other nonsense before leaving this one to you.
The Bris is a physical symbol of the relationship between G-d and the Jewish people. It is a constant reminder of what the Jewish mission entails (a reminder which men need more than women). Let's look at its details:
If circumcision is what G-d wants, why aren't we born circumcised?
G-d created the world imperfect, and gave us the mission to perfect it. G-d created wheat, humans make bread. G-d created a jungle, humans create civilisation. The raw materials are given to us, and we are to use our ingenuity to improve on the world that we were born into. This is symbolised by the Bris - we are born uncircumcised, and it is up to us to "finish the job". This is also true metaphorically. We each have instincts and natural tendencies that are inborn, but need to be refined. "I was born that way" does not excuse immoral behaviour - we are to cut away any negative traits, no matter how innate they may seem.
Why on earth would G-d choose circumcision to represent something sacred?!
Jewish spirituality is about making the physical world holy. The way we eat, sleep, work and procreate should be imbued with the same holiness as the way we pray; our homes should be as sanctified as our synagogues. We find G-d on earth just as much (and perhaps more) than in the heavens. So we put a sign on the most physical and potentially lowly organ, to say that it can and should be used in a holy way. In fact, it is in sexuality that we can touch the deepest part of our soul, when we approach it with holiness.
Why circumcise a baby? Wouldn't the statement be more powerful if it were made by a mature adult?
The circumcision is performed when a child is still not aware of what is happening. This is because the Jewish connection to G-d is intrinsic - whether our minds believe in G-d or not, whether our hearts love G-d or not, our souls know G-d. We can join the covenant with G-d even without being consciously aware of Him, because subconsciously we already know Him.
Why specifically on the eighth day?
The number seven represents nature - seven days of the week, seven colours of the rainbow, seven musical notes (doh re mi etc); the number eight is the number that surpasses seven, and thus represents the miraculous, what is beyond nature. We do the Bris on the eighth day because the Jewish people survive on miracles. Our history defies the laws of nature. We welcome a new Jewish child into this miraculous existence on the eighth day of his life, as if to say, "Expect miracles!"