Reading Systematic Theology with Wayne Grudem – The Existence of God: How do we know that God exists?

This post is part of a 50+ post series from the classic work by Wayne Grudem (PhD, Cambridge), Systematic Theology: An Introduction to Biblical Doctrine. The aim of each post is to provide an overview of each chapter in the book and related resources for each topic.

Synopsis of Chapter

In Chapter 9, Wayne Grudem discusses how we know God exists. There are both internal and external evidences for the existence of God. Beginning with the internal evidence, God made plain his existence to all people including unbelievers (Romans 1:19). Everyone may not admit to God’s existence through the internal witness, but it is not because God hasn’t shown it to them.

In addition, God has given external evidence in both Scripture and nature. The Bible, being a book about God and how he relates to people, is full of affirmations on the existence of God. In addition to the Biblical evidence, God has shown himself through nature. Psalm 19:1-2 declares, “the heavens declare the glory of God, and the sky above proclaims his handiwork. Day to day pours out speech, and night to night reveals knowledge.”

Finally, Grudem covers the traditional proofs for the existence of God like the cosmological argument. Although these arguments are often convincing, people are not naturally disposed to believe them unless convinced by the Holy Spirit. That is why God must remove spiritual blindness from the unbeliever before they can see the light of the gospel (2 Corinthians 4:4).  

All People Have An Inner Sense of God

Everybody knows God exists at some level. The Bible is so adamant about the existence of God, it declares “the fool says in his heart there is no God.” (Psalm 14:1, 53:1). So the Bible doesn’t deny the reality of atheists, but it does tie wickedness (Psalm 10:3-4) and willful rejection of the truth (Romans 1:18) to those who deny God’s existence. 

After conversion, the Christian enjoys a growing sense of God’s presence. People, who were once estranged from God, were spiritually separated from the source of all meaning and life in the universe. Then the Christian is reconciled to God. He or she is adopted into God’s family and can now even call God “Father” because of the new relationship (Romans 8:15).    

Evidence for God Found In Scripture & Nature

The Bible assures us there is a God. From its first verse, the Scriptures declare to us, “In the beginning God created the heavens and the earth” (Genesis 1:1). Later chapters and books unveil his nature and work in creation. Throughout the Bible, God’s existence is assumed not argued for. Even his character is evident according to the Apostle Paul: “For his invisible attributes, namely, his eternal power and divine nature, have been clearly perceived, ever since the creation of the world, in the things that have been made” (Romans 1:20). So God’s existence is understood through our personal experience with God.  

But God was not content to just tell us about himself individually. The creation also declares God’s existence to everyone. Known as the argument from nature or natural theology, God is revealed in the things he created – in those “things that have been made” (Romans 1:20). God made everything. That means his imprint will be on every snowflake, thunderstorm, refreshment from a taste of cold water, joy from a newborn baby, and every other thing he made.     

“Proofs” For The Existence of God

Aside from the inner sense and external evidence for the existence of God, philosophers have constructed various “proofs” for the existence of God. These traditional proofs attempt to get people to think rationally about how God necessarily exists. 

The classic arguments for the existence of God include:

  • The cosmological argument suggests that every known thing in the universe has a cause. The greatest known thing is the universe and only God could cause the universe.
  • The teleological argument argues that the harmony and order of the universe points to design. This design gives evidence for an intelligent purpose or telos (Greek: end / goal). Since the universe was designed with a purpose, there must be an intelligent designer who created it that way – that designer is God.
  • The ontological argument starts with the idea of God is a being “greater than which nothing can be imagined.” Since existence must belong to such a great being, that being must exist.
  • The moral argument begins with everyone’s sense of right, wrong, and desire for justice. This argument then proceeds to base these concepts in the character of God who gave us his moral laws. 

In all of these proofs, some people are convinced and others are not. They are valid in the sense the premises imply their conclusion. However, they are not valid in the sense they do not compel universal agreement. In either case, the classic proofs point people to God’s existence from a more philosophical angle. 

Conclusion: The Holy Spirit Must Convince us To Repent & Believe

God exists. This is clear through many internal, external, and philosophical reasons. However, because of spiritual blindness in unbelievers (2 Corinthians 4:4), only God can persuade people to believe in him. In this sinful world, human persuasion is not enough to convince people to believe in God, to repent of their sins, and to put their trust in Christ. Only God, through his Holy Spirit, can convince people about his existence and their need for a savior.   

For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who by their unrighteousness suppress the truth. 19 For what can be known about God is plain to them, because God has shown it to them. For his invisible attributes, namely, his eternal power and divine nature, have been clearly perceived, ever since the creation of the world, in the things that have been made. So they are without excuse. For although they knew God, they did not honor him as God or give thanks to him, but they became futile in their thinking, and their foolish hearts were darkened. Romans 1:18-21

Special Terms

  • cosmological argument
  • inner sense of God
  • moral argument
  • ontological argument
  • teleological argument

Resources: Wayne Grudem

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