Apophatic theology is a way to describe God by identifying what He is not. It is also known as negative theology.
Apophatic theology – What is it?
Church theologians such as Tertullian, St. Cyril of Jerusalem, and the Cappadocian Fathers popularized this way of identifying God's characteristics, but it was Pseudo-Dionysius who was most influential. Thomas Aquinas quoted Dionysius repeatedly (as many as 1,760 times!) in his Summa Theologica. Aquinas did not rely solely on an apophatic approach, but also employed cataphatic approaches—identifying God through what He is.
C.S. Lewis condoned an apophatic approach for those just learning about Christianity as sort of a cleansing exercise. For example, identify God as not mythology, not analogous, and not like any other being we've read or heard about to get started in understanding the true God.
Many of the ways in which we describe God include an apophatic aspect. For example, when we say that God is Spirit, we are also saying that God is not a physical being. Similarly, saying that God is infinite is to claim that He is not finite.
Both an apophatic approach and a cataphatic approach can be helpful. God is revealed in Christianity and desires to be known. He is also beyond our comprehension. It is appropriate to speak both of what God is and of what He is not. When emphasis is put on one approach over all others, faith can get out of balance.
When theologians and others pit one approach against another, the debate often boils down to God's immanence (His direct involvement with His creation) and His transcendence (His enormous uniqueness, making it difficult for humans to grasp). The truth of the Bible shows us that God is both immanent and transcendent. Thus it is appropriate both to make positive statements about God in the ways He has revealed Himself to us and negative statements about God (i.e., what He is not; apophatic theology) in His transcendence. Remember, too, that when we apply attributes to God such as His love, grace, or mercy, we understand these attributes to be perfect in Him. God's love is much greater than human love, and we apply the attribution of love to God analogically (from the lesser (humans) to the greater (God)).
It is vital to grasp God's great desire to be in relationship with people. He wants to be known and has gone to great lengths to reveal Himself through the Bible, and through His Son, Jesus Christ. Studying who He is both by who He has revealed Himself to be and by clarifying who/what He is not is useful.
Negative theology – What is it?
What is the academic field of Biblical Theology?
How does systematic theology work?
What is general revelation? What is special revelation?
How do we know if a doctrine is really biblical?
Truth about Theology