How do we know who God is or that He even exists? John Wisdom wrote a parable about an invisible gardener to illustrate the argument over God's existence. Two people return to a long neglected garden and to their surprise find some vigorous plants growing among the weeds. The believer says, "There must be a gardener whose been coming to take care of the plants. "The skeptic disbelieves and points to the weeds. They pitch their tents and watch, but they see no gardener. The believer eventually concludes that the gardener must be invisible, leaves no scent, and makes no sound. The skeptic asks how this differs from an imaginary gardener.
A real life example of this argument over God's existence was when astronaut John Glenn responded to Soviet cosmonaut Titov. Titov said he "saw neither angels or gods" while in orbit, and that he did not believe in God. A week later, John Glenn responded, "To look out at this kind of creation and not believe in God is to me impossible. It just strengthens my faith."
Even when one accepts creation as the explanation for the origin of the universe, questions remain. "Why is God invisible?" What is the difference between an invisible God and an imaginary one? Can we know anything about God?
Much of our universe is also invisible. The universe is much larger than we can see. We continue to enlarge the amount of universe we see with better telescopes, and telescopes that sense the electromagnetic spectra not visible to our eyes. We haven't mapped every galaxy in our universe. Even what we have seen on other planets in our solar system is limited, much less planets in other solar systems.
Not only is the full extent of the macroscopic universe beyond our vision, but also the microscopic. We developed techniques such as electron microscopes and atomic force microscopes to view what is too small to see with visible light. We developed techniques for detecting subatomic particles, but have evidence that even smaller particles make up electrons, protons, and neutrons. Even an end to the microscopic world isn't in sight.
What is the best way for God to reveal Himself in terms we can understand? If God were to become human and live with us, then we could understand Him by how He lived. That is what God did as Jesus Christ.
Not only is much within our universe invisible. Much of who we are is invisible to the rest of humanity. Not only do we need to ask, "How can I know God?" but also, "How can I know who I am?" We cannot completely explain ourselves in terms of the physical world. While we continue to progress in neurology and explain more of the mind in terms of the brain, much of the mind eludes explaining and is the subject of debate. An inexplicable aspect of the mind is the ability to choose. One attempt to explain choice in terms of probability is parallel universes for each possible decision one can make. In another universe, the person makes the different decision and lives accordingly. While this parallel universe theory isn't as widely considered possible as the one explaining the fine-tuning of cosmic mass density, it points the same way to the problem with choice.
A practical aspect of the mind being invisible is the distinction between how a person appears to other people and the mind. It's easy to consider outward appearance as most important. This thinking disconnects actions from the mind, from thoughts, motives, and emotions. It leads to one acting out a part that may not reflect what one thinks or feels and doesn't reveal one's motives. The Scriptures reveal that God sees the inner person not just the external (1 Samuel 16:7). If a person wants to do wrong, but is forced to do right, is that person good? For a person to be good, he must want to be good. The book of Job deals with whether Job will do good for the sake of being good without receiving a reward for doing so. Even when it appears Job is about to die, while his wife and closest friends fail to encourage him, Job maintains his integrity (Job 2:6-10). Of his family and friends, Job alone passes the test and passes without even knowing he was tested (Job 42:7-10).
Learning self-motivation to do right, rather than needing external motivation, is an important purpose for our life. People are born with the instincts for self-preservation and reproduction, but those desires don't stop with self-preservation or reproduction. The desire remains to amass wealth beyond necessities. The desire remains to eat beyond the point of being healthy. Sexual attraction isn't restricted to husband and wife, and reproduction is seldom its primary motive. Violence far exceeds self-defense. People struggle with many desires, which have a purpose in their proper place, but motivate them to actions that neither satisfy their desires nor meet their purpose.
Rules and laws can help establish a standard for right, but they don't give someone the desire to do right. They don't even necessarily get someone to act in line with the purpose of the law. People may seek to evade the law without breaking it, or even break it in such a way to avoid the penalty.
While rewards and punishment are important methods for teaching small children, good parents desire for their children to be self-motivated. The most effective way for children to learn includes setting a good example. Similarly, God's most complete revelation of Himself is His becoming the man, Jesus Christ. As Jesus, God experienced all the same human desires we do, but lived as God wants us to live. He is the ultimate example of how to live.
However, Jesus' most important accomplishment was to pay the penalty for our sin (our falling short of good). God highly values this accomplishment, but we don't understand it well. As with goodness, God doesn't force this atoning gift upon us, we must accept it. God's atoning gift transforms our lifestyle from opposing God to cooperating with Him. God adopts us similar to how people adopt children. Just as a good parent seeks to direct a child towards moral goodness, God does the same with us. The goal is more than getting us to behave properly. It's to build good character. It's for us to behave properly because we want to behave that way.God has freed us from the penalty of sin to follow Him out of love rather than fear of punishment.
When we receive Christ's atonement, we also receive Christ, living within us through the Holy Spirit. The Spirit desires good and opposes our inborn selfish desires. The Spirit doesn't override our desires, but gives us ability to desire good. It's up to us to follow the desires of the Spirit and put aside selfish desires. Because selfishness can cloud our thinking, an external written source, the Bible, gives us a standard to test the spirits and distinguish which desires are consistent with God's will.
While God has communicated to us through the Bible, our primary means of communicating with God is prayer. Prayer is for our benefit because God already knows our thoughts, but prayer is more than meditation. God knows what we need better than we do, but often He wants us to ask. Prayer gives Him the opportunity to show Himself though His working in our lives. We must ask to recognize that work is His.
The sign God gave Moses so he would know God sent him was that he would bring Israel out of Egypt to worship God on the same mountain where God spoke to him (Exodus 3:12). Later when Moses was there with the people, he asked God to let him see Him (Exodus 33:17-18). God only allowed Moses to see His back (Exodus 33:19-23). We cannot see God's face, what He will do in the future. We seldom recognize what He is doing now. We best recognize God when we look back and see what He has done.Note: I took this approach to answer the philosophical question, "Why is God invisible?" This is not how I would approach a systematic theology.