In mankind's history there can be found natural theology which is generally characterized as the attempt to establish religious truths by rational argument and without reliance upon alleged revelations. Newt to it we may find lots of name-Christians trying to proof God exist but for them Jesus being God, others can see that their idea of God being Eternal, Immaterial, Transcending space, The Creator and Designer of the universe, Omnipotent, Omniscient, The unique greatest possible Being, does not fit at all their Jesus-god. Many people putting 2 and 2 together decide then wrongly because those qualities not fitting Jesus, he is not being able to be God but then there than also not being a Supreme God.
Though many things may be very difficult to proof that does not mean that they would not exist. Also feelings and experiences are difficult to proof, though the results of a God-Being in our life is something what many feel. One thing is for sure: "If God does not exist, then everything is permitted". In the transcendent reality we can not see nor fully understand God but somehow looking around us and listening to our inner feeling each person should be able to come to recognise the Supreme Power and to understand that reality is shaped by a Power beyond us.