:salamext:
Nerd, the Prophetic guidance explains these factors. So if it's stated in one hadith or verse from the Qur'an that 'so and so' needs to be done. Then we do that.
Along with that, another authentic hadith may be put forward to us, which then explains that removing the foreskin is an Islamic practise, and since we believe in Allaah and His Messenger (peace be upon him) - we follow them and put it into practise.
There may be some verses in the Qur'an where it's stated that there is no intercession, then in another verse or hadith it may be stated that there is no intercession
except which Allaah has willed (i.e. of the righteous etc. on the Day of Judgement.)
So we see that the Qur'an and Authentic Sunnah explain each other.
I'll allow you to keep this point in mind since it is quite useful to understand;
1) Allaah created us with the ability to see, hear, smell, taste, touch etc.
2) Using the above attributes, He allowed us to have the logic of reason and understanding of the things around us. This can also be called 'science.'
This is where those who disbelieve in Allaah stopped, i.e. at 1 and 2.
3) Allaah revealed the revelation to His Messengers' on areas where mankind differed [especially in regard to the confusion they had on step 2.]
This revelation cleared up the doubts and united the people on one understanding, whereas without the revelation - they opposed each other due to a lack of common ground in their understandings of worldly matters, aswell as other matters such as the purpose of life etc.
Even if something doesn't fit in with our understanding on step 3, that's because we may not understand it yet. But since we believe in Allaah and His Messenger, this then allows us to follow it, even if we don't know the true wisdom behind it. Since step 3 is way ahead of step 2. And step 2 can only catch up with step 3 if it can become so advanced, if not now - maybe in the future.
Sorry for dragging it on abit, but here's a link on circumcision and the Islamic stance to it;
http://www.islam-qa.com/index.php?ref=20015&ln=eng&txt=
Allaah knows best.