People say that it's a circular argument that us "fundamentalist Bible believing" Christians use to talk about the existence of God: Why do I believe In God? The Bible says so. Why believe the Bible? Because it's the Word of God. What makes you so sure God wrote it? Because, ultimately, the Bible says so - that's a circular argument all right, but I don't think that a Christian needs to be ashamed or guarded about it.
Sure, the Bible can be historically verified is internally consistent. Sure scriptural prophecies have stood times test. But for someone does not believe, what good does all of that do? Because some of these discussions are so far back in time that no one of us was there - all we have is the Bible - God's word that it happened.
"Faith comes by hearing the word of God". Ultimately, discussions away from the Word of God will lead nowhere, and the danger is that the authority of Scripture is undermined, traded for the wisdom of man - much of which is helpful, but just not Divine Decree.
It's hard to comprehend from an outsiders perspective, how such an approach is inviting or even desirable for anyone who does not have the same presuppositions. But I believe we have no reason to apologise, or rationalise or be diffident about the claims of God on men. There is definitely a measure of gentleness and love and compassion and understanding and relevance - this piece is not about those issues - Francis Shaeffer has got good things to say about the right approach in "taking the roof off" someone's worldview. Ultimately the only word that will save is the Word of Power - and only God's Word, Scripture, the Bible, has power to save.
ESV, Romans 1:16-17
16 For I am not ashamed of the gospel, for it is the power of God for salvation to everyone who believes, to the Jew first and also to the Greek. 17 For in it the righteousness of God is revealed from faith for faith, [4] as it is written, ÂThe righteous shall live by faith.Â
Who speaks from a position of power? Is man justified in his questions about God? Let's get our perspectives right. God owes no man:
ESV, Romans 1:19-20
18 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. 20 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.
Circular arguments are OK, in my book, when they are backed by the clear mandate of God's word. It's not God who has to explain himself or prove himself. It's man who stands judged, because what is plain to him, he has suppressed, and has left himself no excuse.