Allah ﷻ - Understanding His Existence, Divine Names & Actions
A simple argument of His existence.
Once a clever person asked an illiterate Bedouin, “How do you know that Allah ﷻ exists?” The Bedouin pointed his finger towards a camel's dung on the sand and asked that man “What is that?” The man replied “a camels dung” The Bedouin then replied, “If that dung is a proof of camels existence then this entire universe is a proof that Allah exists."
There is a possible divine reason why some people do not believe in the existence of a Creator. In a hadith-e-qudsi Prophet ﷺ narrated to us from Allah: ﷻ “I am as My servant thinks about Me, and I am with him as he remembers Me. And if he remembers Me in his heart, I also remember him in My Heart”. One of the leading Islamic scholar Sheikh Hamza Yusuf says that ‘I am as my servant thinks about Me’ teaches us that He is as we humans perceive Him, which means if we perceive Him to be in existence then indeed He will be in our hearts and close to us and that is the perception of a believer. However, if those who believe Him to be nonexistent then for them He will not exist! Those who forget Allah ﷻ and do not believe in His existence, then Allah ﷻ makes them forget about Him and themselves: “who are oblivious of God, and whom He therefore causes to be oblivious of their own selves.” This being as a result of the natural law of cause and effect that Allah ﷻ has decreed which comes in to play based on the use of our God given free-will, and not predestination.
 Sahih Muslim - Kitab Az Zikr
 Al Quran 59:19 – Asad Translation.