If a Christian, and especially a Jehovah's Witness, is asked to provide proof of the existence of God, it is very likely that he will quote verse four of the third chapter of the letter to the Hebrews, "every house is constructed by someone, but the one who constructed all things is God".
The reasoning may be right, nothing came from nothing but everything on earth is due to the will of a designer, it is still good to note that Paul was not trying to argue about the existence of a Creator. He spoke to his Hebrew Christian companions who certainly did not question the fact that the universe was ruled by a powerful being who is behind everything. Moreover, in antiquity the problem was certainly not the non-belief in God but rather the opposite: people tended to believe in a multitude of gods. Furthermore, Paul, on one occasion, noticed that an altar dedicated to an unknown god had been made, certainly for fear of forgetting to revere a deity.