The early Muslim scholars did not even have to address the issue of the Existence of God, for it was a blatantly obvious fact, which nobody questioned. It was only around the fourth century after the Prophet’s migration to Madinah, when people’s doctrine started being infiltrated with atheism and permeated by unbelief that the scholars had to address the issue.
How does one acquire knowledge of and belief in God, His Attributes, His Law and the Day of Judgment?
Who are Allah’s Messengers? Why are they sent down and what role and functions do they perform? How are they a divine favour for the believers?
What are the pillars of faith? What was the fate of the people of Prophet Lut? What are the characteristics of the Arabic letters?
What is the meant by the record book that each person will receive on the Day of Judgment?