A lot of people had denied the existence of God because they said that there is no evidence that can prove that He is real. On the other hand, there are also people who already believes in Him but failed to live the Christian life.
I know that it is hard to convince the blind to believe the scriptures, how much more if we ask them to pray. But in the contrary, I believe that God can make impossible things possible in His time. I just pray that it would be not too late for them to repent and that they could still have time to enjoy the wonderful life of being a Christian. I don't want to argue with them anymore but I hope they would take time to think about what Jesus said in Matthew 25:13, "Watch out, then, because you do not know the day or the hour."
How about our brothers and sisters who failed to build a tight relationship with our Father?
I've heard people who said that the Bible is boring, praying makes them sleepy, they are attending mass every Sunday and, of course, they already believe that God is there. Being a Christian is not merely about involving your self in a religion and following what your religion is telling you to do, like going to Church every Sunday or offering a part of your income.
Christianity is building a relationship with God. Think about the things that you do to show your affection to the girl/boy that you like. Do that to God! Spend time with Him. Talk to Him. A good relationship takes time and effort to build. And always remember that our Father is already on our way, waiting to meet us. He had sent a thousand of ways to help us build that relationship with Him. God is a humble and a giving Father. Jesus said in Matthew 7:7, "Ask, and you will receive; seek, and you will find; knock, and the door will be opened to you."
Know God through the Bible. In Sirach 6:32-33 He said, "My child you can learn if you want to. You can be clever if you are determined to be. If you are willing to listen, you will learn and become wise." and in Sirach 6:37 He is encouraging you by saying "Devote all your time to studying the Lord's commands and thinking about them. He will give you the insight and wisdom you are looking for."