The existence of God looks like an obvious truth to the believers, but to the non-believers it is, as if covered with seven veils. I have gathered some points from every day logic and some from historical prospective to provide a base to prove existence of God to the non-believers. I understand that each point that follows could be a topic for discussion, but I have tried my best to put as much as possible in a limited space.
1. All RELIGIONS BELIEVE IN GOD Its an undeniable fact that all the religions on this earth claim to be from GOD. Hadhrat Muhammad (SAW), Moses, Jesus, Krishna, Buddha, Baba Nanak and every religious leader taught people to believe and worship GOD. Although all religions have slight differences in the attributes they ascribe to God, but all the religions hold the common view that there is a God who has created this universe. History tells us that even those ancient religions that no longer exist in this world, they also held the view of God, whether they were in ancient America, or in jungles of Africa or in England, or in Java or Sumatra, or in Japan and China or in Siberia or in India. It is an important point that what's the reason for this thought provoking unity among so varied religions? In the ancient times people were not linked together through any means of communication or transport, then how is it possible that people living in isolation thousands of mile away from each other, held the common view about the existence of God? Many of the lands were even not discovered at that time.Even now it is difficult for two persons to completely agree on any issue, then how come this universal unanimity regarding existence of God? All these facts lead us to the only possible conclusion that not only there is a living God but also that God has always manifested Himself through some means to his men to make them believe in Him. Historians agree that if there is such universal unanimity about any issue then there is no reason to disagree with it. Another fact worth noting is that there have been a small number of atheists all the times, this proves that the 'existence of God' is not related to any psychological need of human beings. In this world, one can lead ones life without acknowledging the existence of God, though he will be attempting to close his eyes to the very obvious and clear truth.
2. WHO ARE THOSE WHO CALL PEOPLE TOWARDS GOD? If we look at the life of all those men, who have called other people towards God, we find a surprising common thing about all of them, that they were very pious and righteous men. They were the people who were respected in their nations. They were true people, who spent their lives to guide people to the right path. They persuaded people to shun oppressing others. They taught to look after the poor and needy. They fought all their life against the unjust rulers of the time. They were invariably opposed by the people in power at that time, although They were highly honoured and valued for the purity of their character, even by those who later, on the announcement of their claims, became their enemies. It is inconceivable that those who did not lie about men, began suddenly to lie about God. They were the people whose lives were exemplary for others. Whether it is Indian Krishna, or Irani Zoroaster or Egyptian Moses, or Israelite Christ or Punjabi Baba Nanak, or Leader of the righteous Muhammad (SAW) who was given the title of Trustworthy by his nation from his very youth and who challenged his nation that he had led all of his life among them and Could they point out to any single lie or felony in his life? So all these righteous persons who came to this world at different times and places, all of them say one thing in common... "There is a GOD.... There is a GOD...." Not only they claimed that there is a God but also they claimed that He talked to them.
One may find great philosophers or scholars in the world who have done great works, but their work cannot be compared to the work of those righteous persons. Actually if we study the lives of those philosophers we find that no great deeds compared to their lofty sayings. Why is it that these great philosophers were not able to exhibit that righteousness which was shown by people from GOD? The people whose names I have mentioned above, all of them faced great hardships in the life due to their teachings but nothing could lead them astray from the true path. Their killings were planned, they were exiled from their homes and they were boycotted, but they never gave up their beliefs. Why did not they tell lie and relieve themselves from those hardships that were imposed on them just because of their true belief in God. Their lack of interest in material desires proves it that they were selfless people. When such truthful and trustworthy people are saying it in unison, that they have met with God, they have listened His voice and they have experienced his manifestations, then it really leaves us with no doubt. Even in this material world the people whom we know that they are habitual liars, when they go to a court and speak something under an oath, they are believed, then why don't we believe in those righteous persons?
(source:alislam.org)