The Big Bang theory does not preclude creationism or intelligent design. It is merely a theory based on observable facts about our universe today. As Hubble discovered, and has been proven since, distant galaxies are moving away from us. The farther away a galaxy is, the faster it is moving. This expansion of space implies an early force, a bang, that provided this momentum. But physicists are nearly unanimous in agreeing that the details of what was there before the expansion took place are not knowable by current scientific methods. In other words, the bang part of the Big Bang theory is something that occurred early in universal history, but is not the source of the universe.
Regardless of one's theological convictions, unless one wants to do away with science all together, theories will come about as a necessary consequence of our scientific observations of the reality around us. Seen in this light, which is the way trod by the early religious scientists and their secular brethren, cosmological theories like the Big Bang are merely ways of arranging our observations into a coherent explanation, and are not an attempt to supplant religion or an Absolute Truth/Supreme Being.
