I just picked up Alvin Plantinga’s 1973 book God, Freedom, and Evil. His intent is to discuss “and exemplify the philosophy of religion, or philosophical reflection on central themes of religion.” As I was reading Dr. Plantinga’s definition of Natural Theology, I was reminded of half  of my purpose for starting this blog…
One important aspect of philosophy of religion concerns this latter belief–the belief that God exists, that there really is a being of the sort theists claim to worship and trust. This belief, however, has not been universally accepted. Many have rejected it; some have claimed that it is plainly false and that it is irrational to accept it. By way of response some theologians and theistic philosophers have tried to give successful arguments or proofs for the existence of God. This enterprise is called natural theology. The natural theologian does not, typically, offer his arguments in order to convince people of God’s existence; and in fact few who accept theistic belief do so because they find such an argument compelling. Instead the typical function of natural theology has been to show that religious belief is rationally acceptable. 
Much of the case against faith today is rooted in the belief that faith is irrational. You see it in politics, Hollywood and even science–the middle part of America, where faith is the strongest, is often depicted as the ignorant part. I flatly reject this notion. In fact, I believe the opposite is true. To disbelieve in the existence of God one must reject (or ignore) a great amount of evidence such as the resurrection, the fine-tuning of the universe, the origin and complexity of life, the origin of the mind, the freedom of the will, the universality and objectivity of morals etc. No, it isn’t irrational to have faith in a divine, benevolent, loving, sacrificial, creator God. It is irrational (and in some cases dangerous) to reject Him.
 Half of my purpose is described in the post (faith is reasonable). The other half of my purpose is to glorify God.
 Alvin Plantinga, God, Freedom, and Evil (William B. Eerdmans Publishing Company, Grand Rapids, MI: 1977) Kindle Location 35-40.