Wrapping our minds around the concept of God’s self-existence is about as hard as wrapping our minds around the concept of infinity or eternity.
Our experience is one of creation. We are created beings living in a created world, in a created universe, and we don’t know anything outside of the created existence that we experience. Well, we don’t know anything outside of created existence except God.
God does not live in our created experience. He is the one who created it. In order for God to have created us, and our universe, He has to exist outside of it.
I think of it as if all of creation - our universe, and everything in it - is like a fish bowl sitting in God’s kitchen. God created the fish bowl, and He created everything in the fish bowl - including us. But God does not live in the fish bowl, He just maintains it by feeding the fish. And, to be clear, God does not have a kitchen; God is the kitchen. God is everything, and we exist in Him.
To us it seems as though everything that exists must exist within the fish bowl, because that’s all we know. We can glimpse, dimly, that there is something beyond the fish bowl, but it’s much easier and natural to focus on what’s going on inside of it. But God’s side of the fish bowl exists in the land of infinity and eternity.
To say that God is self-existent is like saying that He is eternal. He just IS. He has no beginning or end. He always was, and always will be, and He doesn’t need anything that He does not already possess within Himself.
We experience lack, need, want, dis-satisfaction, frustration, disappointment, loss, etc… But God does not. God is complete in and of Himself. God is blessed, happy, joyful, fulfilled, satisfied, perfect. God is not limited or constrained like we are. God doesn’t just have everything He needs. He IS everything He needs.
We exist because God created us. But there is no “because” behind God’s existence. God exists.
Remember that eternity exists outside of time - or you could say that it is timeless. And God is eternal. God’s existence does not have a beginning, and cannot have an end. Just like eternity does not submit itself to the ideas of past and future, neither does God. Eternity is the timeless now, And God, being eternal, is the causeless I AM.
How can you know that God exists if you cannot sufficiently argue, or reason, or prove it with an experiment? Knowing that God exists is like being in love. You cannot argue, or reason, or prove it with an experiment. You just know it, and anyone who argues with you immediately looks foolish to you.
To try to explain God’s existence in a way that our minds can fully grasp is to try to put God into the tiny box of our limited understanding. Our minds do not have the capacity to contain all there is to know about God. So, allow your mind to stretch and wrestle with Him until He blesses you, by all means, but give your heart the primary job of knowing and accepting Him. Your heart is far more capable of knowing God than your mind, so don’t let your mind take over in matters that it is not the best equipped to handle.
God will lead you to Himself from your heart, so let your mind follow your heart instead of letting it shut your heart out. Your mind absolutely plays a part in knowing, pursuing, and following God - but your relationship with God is from your spirit first. Your mind cannot know love the same way that your heart can feel it, and God is love. Like a young couple in love, you cannot reason or rationalize with them. Their minds are completely surrendered to their hearts, and nobody can convince them otherwise. This is how you must be in your relationship with God.
Know that He IS. Know that He created you. Know that He has you. Know with your heart that you are His. And then you will be able to know Him.
Exodus 3:14 (NLT) God replied to Moses, "I AM WHO I AM." Say this to the people of Israel: I AM has sent me to you.”
Psalm 90:2 (NLT) Before the mountains were born, before you gave birth to the earth and the world, from beginning to end, you are God.
John 1:1-5 (NASB95) In the beginning was the Word, and the Word was with God, and the Word was God. He was in the beginning with God. All things were made through Him, and without Him nothing was made that was made. In Him was life, and the life was the light of men. The Light shines in the darkness, and the darkness did not comprehend it.
John 5:26 (NASB95) “For just as the Father has life in Himself, even so He gave to the Son also to have life in Himself;
Colossians 1:15-17 (NLT) Christ is the visible image of the invisible God. He existed before anything was created and is supreme over all creation, for through him God created everything in the heavenly realms and on earth. He made the things we can see and the things we can’t see— such as thrones, kingdoms, rulers, and authorities in the unseen world. Everything was created through him and for him. He existed before anything else, and he holds all creation together.