Can we really be certain that God exists? If there is one thing that’s obvious, it is that the existence of God is NOT obvious.

You are right that God's existence is not obvious the way a chair is obvious — and the Bible itself says God hides himself (Isaiah 45:15). What I would question is the step from “not obvious” to “not reasonable.”

1. Certainty is a feeling; proof is a property of arguments. Certainty names a psychological state, and proof names the strength of a case. A person can be utterly certain on thin grounds and can hold a strong argument while feeling unsettled. The question worth asking is not whether the conclusion feels obvious but whether the evidence is good.

2. Most of what you know is not obvious. That the earth orbits the sun is not obvious to the eye — the eye reports the opposite. Germs, plate tectonics, and the age of the universe are all invisible to direct perception and all established by inference. If “not obvious” were a defeater, you would have to surrender most of your knowledge, not just your theological beliefs.

3. The demand for certainty refutes itself. Here is the turn. The principle “believe only what is obvious and indubitable” is not itself obvious or indubitable, and no one has ever derived it without assuming it. Press it and it dissolves: you cannot be certain that certainty is the right standard. A rule that disqualifies itself cannot disqualify God.

4. A cumulative case does not need a knockout. The classical arguments are strongest together. That something exists rather than nothing, that the universe's constants permit life, that consciousness and reason are not obviously byproducts of blind matter, that objective moral obligation is real — each is a strand. A rope of strands holds even when no single strand would.

5. The moral argument is one you already use. When you say torturing a child for fun is really wrong and not merely unfashionable, you are appealing to a standard that outranks human opinion. Paul says that standard is written on the heart, with conscience bearing witness (Romans 2:15). The argument is not that atheists are bad. It is that the moral seriousness both of us share needs a foundation.

6. Scripture claims the evidence is plain, not that conclusions are easy. Paul writes that what can be known about God “is plain to them, because God has shown it to them,” and that his power has been “clearly perceived… in the things that have been made” (Romans 1:19-20). Psalm 19:1 makes the same claim about the sky. The biblical position is not that God is hidden from inquiry but that he is knowable and has been ignored.

7. Why the disagreement, then?. Scripture's answer is suppression, not scarcity: people “did not honor him as God or give thanks” (Romans 1:21). Christians should say that with humility, because it cuts against us too — no one comes to this question neutral, including the believer. It is also not a substitute for argument. It explains why arguments land differently, not why they are bad.

8. Belief can be rational without being inferred. Alvin Plantinga's claim that belief in God may be “properly basic” is worth knowing: some beliefs are warranted without being deduced from other beliefs, the way you trust your memory or your perception of a friend's face. If that is allowed for everything else, it cannot be ruled out in advance only here.

9. What would satisfy you?. This is the honest question to put back. If nothing would count — if any evidence could be explained away — then the position is not a conclusion but a commitment, and it is not more rational than the one you are criticizing. If something would count, name it, and the conversation has somewhere to go.

God's existence is not obvious in the way a chair is, and no honest Christian needs to claim otherwise. But “not obvious” is a fact about perception, not a verdict about evidence — and the demand for certainty is a standard no one, religious or not, actually lives by.

Sources: William Lane Craig, Reasonable Faith; Alvin Plantinga; Edward Feser; Thomas Aquinas.

Related challenges:
• IF God exists, He’s maniacal. If He WANTED to forgive sin, He’s 'all-powerful' and 'all-loving' – He could just, SHAZAM, forgive sin. Instead, He sends down His only Son to be slaughtered and murdered to take care of the sin problem. Now THAT’S evil!
• I hear a lot about “intelligent design.” Has this now proven God and falsified evolution?
• How would you respond to Victor Stenger’s stinging assertion that religious argument leads universally to dismal failure and untold suffering?