Some people have seemingly no interest in this question, and in that case I'd direct you to think about The Great Myth we believe, about The Futility, of Beauty, love etc. Not that I expect these to be entirely persuasive - but might suggest some further consideration is necessary.
When it comes to the question of whether we can know if there is a god.... Some suggest that there must be a god because there must be an uncaused cause at the root of the universe. That at some point something must have made everything. Someone then asks, who made god - and the reply comes, it's like asking who the batchelor's wife is. It's a category mistake, he just is.
One way often appealed to is that there must be an uncaused cause. It's the chicken and the egg defence. Things have to start somewhere, right? Richard Dawkins cites this in The God Delusion (p77) attributes to Thomas Aquinas. "The Uncreated Cause. Nothing is caused by itself. Every effect has a prior cause, and again we are pushed back into regress. This has to be terminated by a first cause, which we call God. "
This argument works on the basis that everything we observe being cause is caused by something. It's an argument from the nature of 'creation'. As a Christian I entirely believe that creation rings out songs about God. The separation of light and dark, sky and earth, land and sea all speak of the unfolding of God's order. The presence of life speaks of the overflow of the trinitarian life of God. Above all else stands humanity. Not special because we're different to the animals but because we're like God. All of these things I see because I already believe in God. All of these support my belief (as they should if its true) but they're not why I hold it in the first place.
The reason I believe in God is because I know him through the Son of God, Jesus. Jesus himself says that only he knows God the Father, Jesus and anyone to whom Jesus makes him known. By Jesus we know God as Father, as the Father of the Son. Jesus is the ultimate prophet who shows us God. He is the Word of God, sent forth to reveal the Father.
The definitive evidence that supports this claim is the historicity of the resurrection of Jesus from death. Christianity is conditioned upon this. Without that then you can write-off everything about Jesus, he's just a dead guy who talked some fine words and a whole lot of manipulative nonsense. With his resurrection there is decent plausibility to say, beyond reasonable doubt, that he is indeed God the Son, through whom we know God the Father. An invitation to know the unoriginate, uncaused-cause isn't all that appealing. A personal invitation to know the Father through his Son is rather different.
See Athanasius, 1650ish years ago in Against the Arians: "...in calling God unoriginate, [the Arians]* are, as I said before, calling Him from His works, and as Maker only and Framer, supposing that hence they may signify that the Word is a work after their own pleasure. But that he who calls God Father, signifies Him from the Son being well aware that if there be a Son, of necessity through that Son all things originate were created. And they, when they call Him Unoriginate, name Him only from His works, and know not the Son any more than the Greeks; but he who calls God Father, names Him from the Word; and knowing the Word, he acknowledges Him to be Framer of all, and understands that through Him all things have been made." (1.33)
*I'm not saying Aquinas, or those who use such logic are all Arians, just that there might be a better way to argue the case.