Christianity holds that God created everything in the universe. Even though various groups attach varying levels of negativity to the natural world, that does not negate the theological fact that God created it. While some focused on the negative, Christian occultists generally focused on the positive: that since God created the world, he meant it to be good, and that if one understands his creation, he will come to better understand God as well. Nature is a second revelation to man, just as the Bible is.
This philosophy refers to the Book of Nature. One "reads" it by studying the natural world and natural principles and understanding how it works and how various pieces relate to other various pieces.