What evidence do we have that Allah ﷻ even exists?

An illiterate Bedouin was once questioned by a clever man: “How do you know that Allah 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.” The logic given by the Bedouin was very simple but extremely thought provoking.

There is a possible divine reason why some people do not believe in the existence of a Creator while others do. In a hadith-e-qudsi Prophet ﷺ narrated to us from Allah: ﷻ “I live in the thought of My servant as he thinks about Me, and I am with him as he remembers Me.”. A leading Islamic scholar Sheikh Hamza Yusuf says that ‘I live in the thought of my servant as he thinks about Me’ teaches us that He is as we humans perceive Him, which means if we believe 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: "We are closer to him than his jugular vein". 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 causes them to forget about Him and themselves: “and be not like those who are oblivious of Allah, 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.