The argument from contingency is a simple five step process that further illuminates the truth of God's existence. Before we list the five points, let us give one example of a contingent being. Lets start with you. You are dependent on many things for your existence. You require oxygen, water, food, etc.... It takes many things for you to exist. These are things that are not contained within yourself. Your body cannot produce its own drinking water. It cannot produce its own oxygen or food. Just as you are contingent on many things outside of yourself for you own existence, so is the universe and everything in it. Whether one talks of plants, animals, automobiles or vacuum cleaners regular maintenance is required and external forces such as food, gas or electricity are required for them to function.
The first point is simply this; If something exists, there must exist what it takes to make that thing to exist. For example, a rock is composed of various compounds. They were necessary to exist before the rock or otherwise the rock never would have come about.
The second point is to point out that the universe does exist. Anyone would grant such an obvious fact.
The third point is that based on our first point, there must exist what it takes for the universe to exist. Something in the universe or from the universe certainly wouldn't have been the cause of the universe. It had to be something outside of the universe that caused the existence of the universe.
The fourth point is that what it takes to create the universe, cannot be a part of or a product of the universe as it is responsible for the existence of the universe.
And the fifth and final point is that the obvious conclusion of the previous four points is that what exists that caused the existence of the universe must transcend the universe. It would not be bound by time or natural laws of the universe because it is not a product of the universe nor is it contingent on the universe.
Someone may claim that this "unknown" that caused the existence of the universe does not necessarily have to be "God." We [theists] claim it is God because the concept of God is the only rational explanation the human mind can muster. There is no other possibility. One could claim a "big bang" started the universe yet there would still have to be reasons the big bang happened. Therefore the "big bang" couldn't have been the first cause. The first cause must be eternal and dependent on nothing. When we finally realize that only one first cause is the start of it all, and that this first cause must have been eternal and contingent on nothing, we are forced to admit that the most logical and obviously compelling possibility to the human mind is the idea of God. Undeniable human history overwhelmingly confirms this last point.