I believe there is a God, and that truth occupies my thoughts more than any other. Belief in some deity seems to have been almost universal before the modern age. Some have said that people have a “sense of the divine” within them. There is something about us and about creation that makes us think about God and to try to find this God (Acts 17:26-27). One of the classic apologetic (argument for God) works is a section of Thomas Aquinas’ Summa Theologica. Aquinas wrote what is now referred to as “The Five Ways”  or reasons why we believe there is a God  (I q.2 a.3 s.c.). The Five Ways are also helpful to aid our understanding of God’s nature as we continue to consider him. 

The first argument that Aquinas offered was the argument from motion. For something to be in motion or to have the potential to be in motion, there must be something to act upon it. Since all creation is in motion or has the potential for motion, then there must be someone who makes everything to be in motion or to have the potential for motion. Aquinas said, “whatever is in motion must be put in motion by another. If that by which it is put in motion be itself put in motion, then this also must needs be put in motion by another, and that by another again. But this cannot go on to infinity, because then there would be no first mover” (STh., I q.2 a.3 resp.). 

Furthermore, this person must always be the fulness of all potential lest we find ourselves without an original cause. Aquinas concluded, “Therefore it is necessary to arrive at a first mover, put in motion by no other; and this everyone understands to be God.” Aquinas went on to argue that 

because the first being must of necessity be in act, and in no way in potentiality. For although in any single thing that passes from potentiality to actuality, the potentiality is prior in time to the actuality; nevertheless, absolutely speaking, actuality is prior to potentiality; for whatever is in potentiality can be reduced into actuality only by some being in actuality. Now it has been already proved that God is the First Being. It is therefore impossible that in God there should be any potentiality.

STh., I q.3 a.1 resp.

Aquinas’ logic is sound and was received by all until the 20th century. Francis Turretin said, “God is a most pure act having no passive admixture and therefore rejecting all composition (because in God there is nothing which needs to be made perfect or can receive perfection from any other, but he is whatever can be and cannot be other than what he is). Whence he is usually described not only by concrete but also by abstract names—life, light, truth, etc.” (Institutes 3.7.5).

Michael Horton, a contemporary theologian, wrote:

Complete and perfect in himself from eternity to eternity, God has no potential that is not already fully realized. God cannot be more infinite, loving, or holy tomorrow than today. If God alone is necessary and independent of all external conditions, fully realized in all of his perfections, then there is literally nothing for God to become. For us, change might be for better or worse, but for a perfect God, change can only yield imperfection.

Michael Horton, The Christian Faith, 235.

This God, who remains without potential, is ontologically necessary to the existence of the universe. This type of God is also the perfect One presented in Scripture. His perfect fullness of life is proven by the way his perfection is manifested to the creation. The divine characteristics of omniscience, omnipotence, and omnipresence are necessities since God is the perfect fullness of life. As Horton said, “The perfection of God’s gifts depends on his own essential perfection. As James reminds us, “Every good gift and every perfect gift is from above, coming down from the Father of lights with whom there is no variation or shadow due to change” (Jas 1:17).” Since God is the first and unmoved Mover, there can be no potential in God, he must be eternally and immutably be the perfect fullness of life-the fullness of being.

This principle is a Scriptural one. Hebrews 3:4 teaches that “every house is built by someone and the builder of all things is God.” Colossians 1:16 affirms that “all things were made by him” and verse 17 further explains that “in him all things hold together.” As we read Genesis 1:1, we find a Biblical claim and a philosophical necessity. All things that have “being” find their existence in the One whose name and essence is “Being”  (Ex. 3:14-15). 

God is the unmoved Mover, first Cause, sufficient Reason, and the necessary Reason of the universe. Since all things are from God, it only follows that all things are for God. As Paul said, “all things are from him and through him and to him” this is why all things should and will praise him forever (Rom. 11:36).